Im trying to add more functionality and tests to our destination plugin API but this because quite hard now when source and plugin reside in the same place and everything is suffixed with `source` or `destination`.

This should make it more "go" idiomatic by splitting `source` and `destination` into two different packages and help with follow-up PRs. 

This is a breaking change but relatively minor one as it is mostly affecting one file in each plugin (the `main.go` or `plugin.go`)

currently we silently drop metrics from child tables. This add them back when root table sync is finished so it is printed once per table/client (and not per object like it was before with millions of log lines)

This is uses correct error codes for gRPC in most places. We use Internal and this is the intedded error code for server errors. This is also used by the grpc server as well but it doesn't mean it is only for the gRPC code. See documentation:

https://pkg.go.dev/google.golang.org/grpc/codes#Code
https://cloud.google.com/apis/design/errors

The right codes for internal error are `Unknown` (The default one) and `Internal`

This neatens the newlines rendered for table docs, so we can no longer get multiple newlines in a row, like here: https://github.com/cloudquery/cloudquery/pull/5547/files#diff-7a51ae50d93ba1ae94ee3a2e3ff898ae0224a0a1cc32cafe0c667ff46cf080e6R1-R8

Closes #454

🤖 I have created a release *beep* *boop*
---


## [1.12.6](v1.12.5...v1.12.6) (2022-12-18)


### Bug Fixes

* Add better logging/metric per table ([#513](#513)) ([da36396](da36396))
* Improve formatting of newlines in markdown files ([#492](#492)) ([e48ff90](e48ff90))
* Include table name in logs on panic ([#505](#505)) ([a0b8a46](a0b8a46))
* Move source & destination plugin code to separate packages ([#516](#516)) ([6733785](6733785))
* Use correct error codes ([#514](#514)) ([8b53d76](8b53d76))

---
This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).