Add git plugin (#2735)

## Summary
Implement Git plugin support for loading plugins from any Git repository
with revision/branch/directory targeting. Extends existing GitHub plugin
functionality to support self-hosted and local Git repositories.
Fix #2048 in a more simple way than #2470 since there is no change in
json schema

## How was it tested?
Manually on a mock project with multiple transport : git+ssh, git+http,
git+file

## Community Contribution License

All community contributions in this pull request are licensed to the
project
maintainers under the terms of the
[Apache 2 License](https://www.apache.org/licenses/LICENSE-2.0).

By creating this pull request, I represent that I have the right to
license the
contributions to the project maintainers under the Apache 2 License as
stated in
the
[Community Contribution
License](https://github.com/jetify-com/opensource/blob/main/CONTRIBUTING.md#community-contribution-license).

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Co-authored-by: John Lago <750845+Lagoja@users.noreply.github.com>