[Feat] - Replace git cmds using os.Exec with go-git or go-github

[abhijith-darshan]

Currently the git commands are being executed using go os.Exec

We can replace this with either go-git or go-github

• This will improve performance in reconciliation loops (no local persistence of repositories that are cloned)
  • parallel reconciliation with MaxConcurrentReconciles
• API based approach will improve security and reduce vulnerabilities that comes with OS / CLI commands

[abhijith-darshan]

@auhlig @databus23 - Wdyt?

govulncheck reports vuln coming from os cmds and moving to API based approach should improve maintenance and improve extensibility