Op slicing upstream refactor (#14832)
### Slice op upstream refactor
A refactor work for https://github.com/microsoft/onnxruntime/pull/13672.
### Motivation and Context
There is a similar optimization opportunity for other operator
upstreaming, to reduce compute flops. So refactor the existing code base
for making it easier to support other ops.
The changes in this PR are mainly about renaming and moving.
- Move common logic (from compute_optimizer.h/cc) into
upstream_transformer_base.h/cc and shared_utils.h/cc.
- For upstream common logic, they are moved into
upstream_transformer_base.h/cc
- For shared utilities, they are moved to shared_utils.h/cc.
- After the move, compute_optimizer.h/cc mainly for upstreaming gather
implementation (inheriting upstream_transformer_base.h/cc). Ideally it
should be renamed, but for easier review this time, I keep its name.
