xref #76378

Problem description

There are too many test configs.

• Whether or not to start a tenant server to run the test's queries:

  • random (default - desirable)
  • always-off
  • always-on

• Which tenant server config to use:

  • Serverless-like config, using a networked KV tenant config + rate limiting - StartTenant()
  • Dedicated-like config - StartSharedProcessTenant()

All these choices results in (currently) 6 different possible test configurations.

In addition to that complexity, some tests ignore the config above and configure their test tenants manually themselves.

In those tests, it's possible to see at run-time both the test tenant created by the test framework, and the test tenant created by the test code, side-by-side. This is confusing.

Expected solution

We want to collapse the selection of whether or not to use a test tenant and which server config to use into just 1 knob with just 2 possible values:

• auto-test-tenant-probabilistically (default):

  • in CCL builds: 30% chance to have no secondary tenant; 30% to use serverless-like config, 30% to use dedicated-like config.
  • in OSS builds: 30% chance to have no secondary tenant; 60% chance to use the dedicated-like config.

• no-auto-test-tenant: no secondary tenant created by the test framework.

The latter setting can have informational variants (like those defined in #106768) to distinguish cases where there's a bug (yet to be fixed) and from cases when the test truly wishes no automatic behavior.

Jira issue: CRDB-29709

Epic CRDB-31933