Support multiple rights vs same left scenario with a simple call to ApiComparer

[safern]

With these changes, comparing the same left against multiple rights is optimized ~30% in time, here are the benchmark results:

Method	Mean	Error	StdDev
UseOneApiCompatPerPath	442.8 ms	5.12 ms	4.79 ms
CompareOnePerSide	107.5 ms	0.64 ms	0.53 ms
UseOneApiCompatOverall	291.4 ms	2.05 ms	1.92 ms

UseOneApiCompatPerPath is invoking ApiComparer.GetDifferences for each combination of (left, right) which takes 442.8ms, vs now with this changes you would only need to do what I do in UseOneApiCompatOverall which calls ApiComparer.GetDifferences once with an IList for the rights, which takes 291.4ms for comparing System.Runtime.dll ref assembly vs System.Runtime.dll implementation with 4 different instances of it, that's a 151ms improvement.

Also, the regular scenario of comparing one left against one right, is about the same, this is before these changes:

Method	Mean	Error	StdDev
CompareOnePerSide	101.7 ms	1.03 ms	0.86 ms

Here are the benchmarks I used to measure this: https://gist.github.com/safern/6a1354ee3e3d1e13272c5c3119a6e466

TODO after this change is being able to customize the NoWarn and IgnoredDifferences for the different rights that are being passed as at the moment it uses the same, which might not be desirable in some cases. I'll address that as part of the error baselining story.

Also, change how the Rules are loaded and invoked, by following a similar model as Roslyn, where an Initialize method is invoked and we pass in a context. Then Rules can register to context callbacks, that way the Rule just register to whatever callbacks it is important to run on based on the Mappers it runs for. This change fixes: #16918

[safern]

I started with this as a Generic type even though it is now currently used with IAssemblySymbol only as this might be useful to use it to store the elements in the mappers and that way we could customize the diagnostic messages using the metadata information for each element in the mapper.

However I don't know if it is too much overhead and instead just have a setting to customize the left and right names when raising diagnostics.