[TRE][NFC] Refactor shared state into member variables.

Separate functions that require shared state into a class to avoid
needing to pass them though multiple functions just to be available
where needed.

The main motivation for this is that we would like to remove the
limitation that accumulator values be dynamic constant, which would
require additional shared state between call eliminations in the same
function, compounding this issue.

Differential Revision: https://reviews.llvm.org/D79299