[ft] Add continue unit test generation workflow

[rohitvinnakota-codecov]

This change lays out the groundwork for running unit tests against code coverage and test analytics metrics to generate better tests for a given PR. The retry unit tests endpoint will be invoked from Codecov's Shelter service

This change also adds a DbPrContextToUnitTestGenerationRunIdMapping table that will store information(owner, repo, etc) + agent context about past runs, which will be leveraged as a memory store for subsequent unit test runs.

Some other updates:

• Fix for an issue where a generated tests PR is based off of the main branch. It should be built on top of the feature branch tests are being requested on
• Update Claude version
• Add logic that lets the codecov-ai GH app post updates instead of autofix under certain conditions

[roaga]

Could you also add some more tests since this is a big PR? We're trying to keep code coverage up in Seer