Modularize bridged provider test setup for re-use

[thomas11]

pulumi/pulumi-aws#3074 uses the extension point extraTests in .ci-mgmt.yaml to add additional tests. That works great, but it required copy-pasting ~17 workflow steps verbatim to get everything set up so tests could run (check out repo, install dependencies, etc.). If this standard setup was extracted into one or more actions similar to, e.g., install in azure-native, it could simply be re-used.

[blampe]

We consolidated the test workflow (#1214), which would make it much more straightforward to run some additional steps. However ultimately extraTests has been removed from AWS because all of these workflows were more appropriately formulated as standard unit or integration tests.

• Lint upstream as a normal unit test pulumi-aws#4918
• Test shim as a normal unit test pulumi-aws#4917
• Simplify OIDC extraTest pulumi-aws#4909

The custom workflows were slow, hard to maintain, and introduced subtle bugs.