Add decoding to section mangler

[CohenArthur]

Needs #1198 and #1199, so only review section_mangler/parser.rs and section_mangler/lib.rs

This PR adds the reverse operation to #1160 and #1198, by parsing the mangled section name and deserializing it into an instance of SectionMangler. This allows the loader to compare two mangled section names easily, and to make certain decisions.

[ghaith]

I think the conflict is just in tests, i'll fix the conflict and merge this
Edit: I can't push to the fork, I think you it's a setting on the PR from your side to allow us to push the fork branch.
@CohenArthur do you mind solving the conflics? It's just a cargo insta accept I'll approve and push right away.

[CohenArthur]

@ghaith no worries, I'll update this PR with fixed conflicts as soon as the previous two are accepted. in the future PRs should be smaller but these were all depending on each other so it was a bit of a mess :) sorry!

The merge-base changed after approval.

The merge-base changed after approval.

[ghaith]

Github does not seem to accept me as reviewer

I'm not sure why that is but i'll check the settings and try again

The merge-base changed after approval.

The merge-base changed after approval.

[CohenArthur]

Updated the source branch once again @ghaith