…ns (#62934)

Migrates Cody Gateway to use the new Enterprise Portal's "read-only"
APIs. For the most part, this is an in-place replacement - a lot of the
diff is in testing and minor changes. Some changes, such as the removal
of model allowlists, were made down the PR stack in
https://github.com/sourcegraph/sourcegraph/pull/62911.

At a high level, we replace the data requested by
`cmd/cody-gateway/internal/dotcom/operations.graphql` and replace it
with Enterprise Portal RPCs:

- `codyaccessv1.GetCodyGatewayAccess`
- `codyaccessv1.ListCodyGatewayAccesses`

Use cases that previously required retrieving the active license tags
now:

1. Use the display name provided by the Cody Access API
https://github.com/sourcegraph/sourcegraph/pull/62968
2. Depend on the connected Enterprise Portal dev instance to only return
dev subscriptions https://github.com/sourcegraph/sourcegraph/pull/62966

Closes https://linear.app/sourcegraph/issue/CORE-98
Related to https://linear.app/sourcegraph/issue/CORE-135
(https://github.com/sourcegraph/sourcegraph/pull/62909,
https://github.com/sourcegraph/sourcegraph/pull/62911)
Related to https://linear.app/sourcegraph/issue/CORE-97

## Local development

This change also adds Enterprise Portal to `sg start dotcom`. For local
development, we set up Cody Gateway to connect to Enterprise Portal such
that zero configuration is needed - all the required secrets are sourced
from the `sourcegrah-local-dev` GCP project automatically when you run
`sg start dotcom`, and local Cody Gateway will talk to local Enterprise
Portal to do the Enterprise subscriptions sync.

This is actually an upgrade from the current experience where you need
to provide Cody Gateway a Sourcegraph user access token to test
Enterprise locally, though the Sourcegraph user access token is still
required for the PLG actor source.

The credential is configured in
https://console.cloud.google.com/security/secret-manager/secret/SG_LOCAL_DEV_SAMS_CLIENT_SECRET/overview?project=sourcegraph-local-dev,
and I've included documentation in the secret annotation about what it
is for and what to do with it:


![image](https://github.com/sourcegraph/sourcegraph/assets/23356519/c61ad4e0-3b75-408d-a930-076a414336fb)

## Rollout plan

I will open PRs to set up the necessary configuration for Cody Gateway
dev and prod. Once reviews taper down I'll cut an image from this branch
and deploy it to Cody Gateway dev, and monitor it closely + do some
manual testing. Once verified, I'll land this change and monitor a
rollout to production.

Cody Gateway dev SAMS client:
sourcegraph/infrastructure#6108
Cody Gateway prod SAMS client update (this one already exists):

```
accounts=> UPDATE idp_clients
SET scopes = scopes || '["enterprise_portal::subscription::read", "enterprise_portal::codyaccess::read"]'::jsonb
WHERE id = 'sams_cid_018ea062-479e-7342-9473-66645e616cbf';
UPDATE 1
accounts=> select name, scopes from idp_clients WHERE name = 'Cody Gateway (prod)';
        name         |                                                              scopes                                                              
---------------------+----------------------------------------------------------------------------------------------------------------------------------
 Cody Gateway (prod) | ["openid", "profile", "email", "offline_access", "enterprise_portal::subscription::read", "enterprise_portal::codyaccess::read"]
(1 row)
```

Configuring the target Enterprise Portal instances:
sourcegraph/infrastructure#6127

## Test plan

Start the new `dotcom` runset, now including Enterprise Portal, and
observe logs from both `enterprise-portal` and `cody-gateway`:

```
sg start dotcom
```

I reused the test plan from
https://github.com/sourcegraph/sourcegraph/pull/62911: set up Cody
Gateway external dependency secrets, then set up an enterprise
subscription + license with a high seat count (for a high quota), and
force a Cody Gateway sync:

```
curl -v -H 'Authorization: bearer sekret' http://localhost:9992/-/actor/sync-all-sources
```

This should indicate the new sync against "local dotcom" fetches the
correct number of actors and whatnot.

Using the local enterprise subscription's access token, we run the QA
test suite:

```sh
$ bazel test --runs_per_test=2 --test_output=all //cmd/cody-gateway/qa:qa_test --test_env=E2E_GATEWAY_ENDPOINT=http://localhost:9992 --test_env=E2E_GATEWAY_TOKEN=$TOKEN
INFO: Analyzed target //cmd/cody-gateway/qa:qa_test (0 packages loaded, 0 targets configured).
INFO: From Testing //cmd/cody-gateway/qa:qa_test (run 1 of 2):
==================== Test output for //cmd/cody-gateway/qa:qa_test (run 1 of 2):
PASS
================================================================================
INFO: From Testing //cmd/cody-gateway/qa:qa_test (run 2 of 2):
==================== Test output for //cmd/cody-gateway/qa:qa_test (run 2 of 2):
PASS
================================================================================
INFO: Found 1 test target...
Target //cmd/cody-gateway/qa:qa_test up-to-date:
  bazel-bin/cmd/cody-gateway/qa/qa_test_/qa_test
Aspect @@rules_rust//rust/private:clippy.bzl%rust_clippy_aspect of //cmd/cody-gateway/qa:qa_test up-to-date (nothing to build)
Aspect @@rules_rust//rust/private:rustfmt.bzl%rustfmt_aspect of //cmd/cody-gateway/qa:qa_test up-to-date (nothing to build)
INFO: Elapsed time: 13.653s, Critical Path: 13.38s
INFO: 7 processes: 1 internal, 6 darwin-sandbox.
INFO: Build completed successfully, 7 total actions
//cmd/cody-gateway/qa:qa_test                                            PASSED in 11.7s
  Stats over 2 runs: max = 11.7s, min = 11.7s, avg = 11.7s, dev = 0.0s

Executed 1 out of 1 test: 1 test passes.
```