Modularize bridged provider test setup for re-use #752
Description
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.