support generating sbom for particular branch using tool method

[viveksahu26]

This PR add the following changes:

• Added support for fetching SBOMs from a specific branch in the GitHub Tool Method.
• Adds the separate flag for branch : in-github-branch.
  • If branch is provided, then it will clone that specific branch and generates SBOM.
  • If branch is not provided, which is by default empty, then in that case, it will pull up repo for default branch

NOTE:

• This branch method only supports for tool method, whereas api and release won't support.

Description:

Why API and Release Methods Don't Support Branch Selection ?

• GitHub API Method: The dependency graph only provides SBOMs for the default branch and does not allow fetching SBOMs for arbitrary branches.
• GitHub Release Method: SBOMs are generated for tagged releases, which are typically based on the main branch and do not support fetching from specific branches.

Why Tool Method Supports Branch Selection ?

• The Tool Method clones the repository locally, allowing us to check out any specific branch and generate an SBOM from that branch using an external tool like Syft.