fix: Refactor C# mutation orchestration to a simpler design

[dupdob]

Redesigned MutationStore and MutationContext classes to a simpler and more consistent design.

Redesigned function/method/accessor/lambda orchestrator via a common parent class. Removed all xxxExpressionToBodyEngine classes.

Fixed following (non reported) bugs:

1. LocalFunction orchestrator may generate invalid local functions by adding erroneous return to void method (can be seen in the old unit test 🤦 )
2. Improved return default injection policy. Those are injected only when:
   • function/method/accessor/lambda in body form
   • of non void (including async Task) return type
   • with at least one return present in the block
   • not ending with a return statement
   • not an iterator function (yield modifiers present)
3. Add proper support for async local functions (not supported before)
4. More consistent handling across methods/functions/accessors...
5. provide support document explaining the purpose of each class used during CSharpOrchestration.

Many classes and lines of code have been removed, and hundreds of documentation lines have been added.

I must say I am quite happy with this one, borderline on proud.
😆

EDIT: obviously the associated documentation refers to this design and not the existing one

[JAKeijzer96]

I reviewed the technical reference doc. Comments are purely regarding grammar/formatting as I have no real knowledge of the Stryker internals (yet..)
In general it's an absolutely amazing write-up which is great for someone who's new to the project such as me. Thanks!

[dupdob]

@JAKeijzer96 : many thanks for the amazing editorial work here!!.
Btw, this document applies to the version in this PR. My initial objective was to write this doc, but I realized the design needed rework when writing it. Simple rule is: if it is hard to document, it can not stay as is.

[richardwerkman]

@dupdob Thanks a lot for this improvement! Mainly the documentation is a real lifesaver, I understand what's going on a lot better now. Some small remarks here and there but I agree with the changes in general

[dupdob]

@richardwerkman : your feedback is most welcomed. And thanks for the taking the time to read all this. This PR is probably no picnic to review

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
91.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud