Update type parameter inference from constraints specification

[agocke]

Align the type parameter inference from constraints proposal with the prototype implementation in dotnet/roslyn#84655.

The updated specification:

• distinguishes ordinary bounds from constraint bounds and gives ordinary bounds precedence;
• excludes reflexive dependencies introduced solely by a self-referential constraint;
• specifies that all type variables selected by the same fixing step are determined from the same inference state before constraint inference occurs;
• defines constraint inference and its recursive bound classification;
• adds examples for ordinary-bound precedence, cyclic dependencies, order independence, and termination; and
• narrows the discussion of potential breaking changes to the behavior the prototype actually introduces.

Champion issue: #9453
Implementation: dotnet/roslyn#84655

[jjonescz]

I assume this split is done for backwards compatibility. Consider noting that somewhere so the intent is clear.

[jjonescz]

I guess it's somewhat mentioned in the Drawbacks section.