Migrate analyzer local state to a structured value lattice

[jtschuster]

Summary

In the analyzer, we see ITupleOperations that could be lowered to ValueTuple construction and destruction, or lowered to assignments to local variables -- but there is no way to know for sure. However, the basic (and relatively common) case of (a, b) = (b, a) should be supported. This requires us to model a Tuple value in dataflow. In the current implementation, we can model it in Deconstruction evaluation, but it's not a first-class concept in the dataflow visitor. This PR stack makes the concept of a Tuple of TValue a first-class concept.

ITupleOperations are treated as Top in the lattice for all cases except for when it is the outer operation on a DeconstructionOperation (i.e. an expression in the form of (a, b) = (b, a)). If the TupleOperation appears elsewhere in the deconstruction (for example, within a ternary that is deconstructed (a, b) = c ? (x, y) : (b, a)), we make no assumption about whether or not a ValueTuple is created.

This PR introduces a recursive LocalValue and its lattice for local state, r-value captures, and hoisted state, while preserving existing deconstruction behavior. This LocalValue implements the first-class support for Tuples of TValue in the dataflow visitor. Also adds equality, deep-copy, and lattice-law tests.

Validation

• Analyzer DataFlow: 85 passed, 2 skipped.
• ILLink DataFlow0: 42 passed; DataFlow1: 41 passed.
• NativeAOT shared ConstructedTypesDataFlow and DeconstructFieldTarget: 2 passed.

Stack layer 2/3, based on the tests-only branch.

Note

This PR was generated with GitHub Copilot assistance.

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