Update IsLocalAddrExpr() to recognize address expressions (lea)

[CarolEidt]

category:cq
theme:basic-cq
skill-level:intermediate
cost:small

[CarolEidt]

This came up in the discussion of PR dotnet/coreclr#4303, which improved the GC barrier check to handle not just ADDR(LCL_VAR) but expressions involving lclVar addresses, using IsLocalAddrExpr().However, it was pointed out that IsLocalAddrExpr() doesn't consider a GT_LEA of a local address to be a local address expression. It should be updated to do so.

[pgavlin]

cc @dotnet/jit-contrib

[mikedn]

Ideally we'd simply get rid of IsLocalAddrExpr. The tree patterns it recognizes should be converted to equivalent single node representations (GT_LCL_VAR/FLD/ADDR). The main roadblock in doing this is being able to express block ops involving local struct fields in IR.