[mlir][AsmPrinter] Change value numbering for local scope to be the next isolated operation.

Summary: This revision updates the value numbering when printing to number from the next parent operation that is isolated from above. This is the highest level to number from that still ensures thread-safety. This revision also changes the behavior of Operator::operator<< to use local scope to avoid thread races when numbering operations.

Differential Revision: https://reviews.llvm.org/D77525