Correctly revise methods defined in external method tables

[serenity4]

Fixes #646.

Requires:

• Support external method tables in method evaluation JuliaDebug/JuliaInterpreter.jl#680
• Add method table as key for method_info JuliaDebug/CodeTracking.jl#140
• methoddef!: use mt => sig format when filling in signatures JuliaDebug/LoweredCodeUtils.jl#125

To do before merging:

• Test this "in the wild" with some large packages (SPIRV.jl and GPUCompiler-dependent packages)
• Update documentation, docstrings and comments.

[timholy]

This looks great. I don't think that #815 offers anything that this doesn't, so this PR could close that one unless you disagree.

[serenity4]

I looked into supporting the mapexpr-form of include, and it doesn't strike me that it would require changes to either CodeTracking or LoweredCodeUtils. I'm not done with that, but it's getting a bit involved and I'm a bit low on time these days.

To avoid leaving this PR rotting for too long I think it might be good to move forward with the release of CodeTracking 2.0 and LoweredCodeUtils 4.0 after JuliaDebug/LoweredCodeUtils.jl#125, so we can merge this PR. Then, if the mapexpr support still eventually requires a new breaking release for either, I would hope the disruption to not be too impactful.

@timholy what do you think?

[serenity4]

Once LoweredCodeUtils v3.4.3 is available in the registry (JuliaRegistries/General#135445), if all checks pass this is good to merge!