Investigate performance of "Create" view

[alexr00]

The "Create PR" view is slow to load and slow to create a PR. We should see if there are opportunities to improve the load performance and the create performance.

[alexr00]

Improvements have been made in the load performance, but there may still be opportunities to improve the create performance.

[alexr00]

Took a look at the performance of the "create" button, there are three chunks where most of the time is spent:

Pushing the branch: ~2.4 seconds
@lszomoru, it's a long shot, but any chance there's a place for performance improvements in the git extension API Repository.push?

Creating the PR using GitHub API: ~1 second
This currently uses the rest API. I'll see if the GraphQL API is any faster.

Writing some metadata to the git config: ~.6 seconds
Not much to be done here.