Refactor integration test workflows for reusability

[jhamon]

Problem

We want to make our integration testing reusable by the platform team, with configurations that allow:

• Targeting staging instead of prod
• Targeting specific environments/regions/clouds
• Running with previously published SDK versions

Solution

• Refactor integration testing CI configs to split into reusable workflows that individually test either serverless features or pod index features. This separation greatly improves the ergonomics of expressing the test matrix for each of these code paths.
• Added setup steps that work when executing the tests using previously published artifacts.
• Added a bunch more test cases that were previously missing.
• Added cleanup step in dependency testing

Type of Change

• Infrastructure change (CI configs, etc)

Test Plan

See tests passing.