Check remote refs instead of local refs when applying/pushing changes

[benbp]

With recent changes to use sparse checkout in our release steps, the assumption that all remote refs will be downloaded to the local git state no longer holds. This updates our git branch push script to check for pre-existing branches via git ls-remote instead, and additionally constrains the git fetch command to only fetch relevant refs.

[azure-sdk]

The following pipelines have been queued for testing:
java - template
java - template - tests
js - template
net - template
net - template - tests
python - template
python - template - tests
You can sign off on the approval gate to test the release stage of each pipeline.
See eng/common workflow

[benbp]

Template pipeline: https://dev.azure.com/azure-sdk/internal/_build/results?buildId=922280&view=logs&j=3209e245-f6ba-5d50-799f-1562c2eae04f&t=37ce2dc7-5e9f-573b-8bc7-a6f98ce6968f

Right now that pipeline exercises the script against a full checkout, since the java repo reverted the sparse checkout. Testing for the latter scenario will gate Azure/azure-sdk-for-java#21912.

[azure-sdk]

The following pipelines have been queued for testing:
java - template
java - template - tests
js - template
net - template
net - template - tests
python - template
python - template - tests
You can sign off on the approval gate to test the release stage of each pipeline.
See eng/common workflow

[ghost]

Hello @azure-sdk!

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