Use sparse checkout for eng/common sync PRs

[benbp]

We're spending 10+ minutes sequentially cloning repos in order to create the patch files for our sync PRs, when those files are localized to a single directory. We could eliminate ~99% of this time by doing a sparse checkout instead.

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[benbp]

/check-enforcer reset

[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

[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

[weshaggard]

Not sure if this change is worth flushing through eng/common but I guess if you are doing the sparse-checkout then it can come along for the ride.

[benbp]

Yeah it's getting lumped in with the pre-existing display name changes. Figured it was easier to just let the whitespace fix tag along (rather than me unstaging this file every time I open it and my editor auto-deletes whitespace).

[ghost]

Hello @azure-sdk!

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