Scan PR - Add option to scan source and most common ancestor target c…

[attiasas]

• All tests passed. If this feature is not already covered by the tests, I added new tests.
• This pull request is on the dev branch.
• I used gofmt for formatting the code before submitting the pull request.
• Update documentation about new features / new supported technologies

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Scan PR/MR command

We are scanning both the source and target branches.
Then we compare the results and filter only those found in the source, not in the target.

The new option calculates the most common ancestor commit by running git merge-base source target, checking out to the commit, and treating it as the target to be merged to.
To use this option you can:

• Specify it as an env var: JF_USE_MOST_COMMON_ANCESTOR_AS_TARGET
• Specify it in Frogbot config: useMostCommonAncestorAsTarget (at Git section)

[eranturgeman]

fix title + consider adding an explanation about when one should use this feature

[eranturgeman]

Where does useMostCommonAncestorAsTarget field be inserted in frogbot-config.yml? is it part of the 'Project' list or a general definition.
We need to consider if we even want to add it as a field to frogbot-config.yml since the config file is going to change soon and maybe we should avoid adding new field to it

In addition, please open a ticket to add this new field to ConfigProfile

[eranturgeman]

Looks good, see my comments

[github-actions]

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