feat(solc): add source map parser

[mattsse]

Motivation

Closes #639

Solution

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[gakonst]

Sourcemap parsing algorithm shared by @MrChico here.

@brockelmore has been using this branch to build out the debugger and it seems to be working correctly so far.

Should we perhaps merge, or have any bugs been detected?

[mattsse]

added test mode that does a roundtrip check for the parsed input/elements, very confident that's correct now @gakonst, same algo as https://gist.github.com/MrChico/fffdf5526b21a99e84f48533f159b540

can be merged imo, @brockelmore?

[brockelmore]

based on my testing this is good to go

[gakonst]

reviewed for idiomatic rust / missing docs and to see if I can follow the code, LGTM. have not reviewed the full algorithm so defer to you guys / your manual testing here.

we'll close the feedback loop with the debugger and coverage features on forge, so any bugs can be uncovered there.