Deleted all of the "experimental" legacy cruft. Felt good.

Made equivalence tests pass for interval parsing.

Added tests for ShimGenerator and changed its behavior a little.

Made the parsing logic use the new shim generator.

Added shim generator to support default parameters in simple parsers. This has a non-trivial cost of effectively making the library CoreCLR only because the code depends on some bugfixes in .NET Core 3 and is dynamically compiled, which hurts ILLinker scenarios and is not supported on all platforms. These concerns will have to be addressed in the future.

Infrastructure for testing parsing + some simple parity tests.

Refactored interval generation. Some preparations for adding parsing tests.

Tuned the generation of doubles and singles. Implemented IFormattable on Interval (including tests).

Fixed up some tests.

Implement invalid boundaries and tests for them.

Fixed the bug with generation of Int32s being weird, and tuned the generation of doubles.

Fixed the bug in Interval.Create and the corresponding test which let custom invalid values through.

Refactored ComparingValues/ToString/GetHashCode so that null is never passed to a custom comparer. All tests are green for the first time in six months.

Refactorings according to the new rules of creating intervals. Added IBoundaryValueComparer

Implemented Interval.Contains, added tests for it and other methods on Interval<T, TComparer> and Interval<T>.