Adding a new merge-sboms sub-command

[a-ovchinnikov]

Functionality for merging SBOMs was already present in the codebase, this commit exposes it to a user.

Maintainers will complete the following section

• [x] Commit messages are descriptive enough
• [x] Code coverage from testing does not decrease and new code is covered
• [x] Docs updated (if applicable)
• [-] Docs links in the code are still valid (if docs were updated)

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[brunoapimentel]

Overall approach LGTM :+1: