Better metric dependency resolution and reuse

[coleramos425]

Describe the suggestion

Better metric dependency resolution and reuse

Justification

Enable re-use of intermediate computations and metrics to avoid code-duplication / copy-paste errors.
For example when looking at the PoP for VALU FLOPs, we:

1. Compute the FLOPs
2. Compute the Peak
3. Recompute the FLOPs and the Peak to find the % of Peak

Other examples would be things like continually recomputing duration, GRBM_GUI_ACTIVE * $numCU, etc., etc.

If we had a more flexible evaluator, we could also theoretically let a user ask for just a specific metric, or group of metrics (and break the "ask for SQ on profile", "ask for section x.y on analyze" chain)

Implementation

Less clear what the best way to do this short of a full AST with dependency resolution would be.
In the short term, we could move more values to the list of builtin vars: https://github.com/AMDResearch/omniperf/blob/ed31b8a988b0fde6a5e11bc949417c82c6db1abc/src/omniperf_analyze/utils/parser.py#L77

Additional Notes

May not be as important if we can pre-compile metrics

Originally posted by @arghdos in #153 (comment)