Add shared const opcode definitions

[guosran]

This PR only adds the shared opcode definitions needed by the const-op RTL fixes. It intentionally does not change any RTL module behavior.

The following module-specific PRs depend on these opcode names:

• DivRTL REM_CONST
• CompRTL const comparisons
• GrantRTL grant_once const
• ShifterRTL const shifts
• ConstQueueDynamicRTL const-op consume tracking
• conv small validation config generation

Validation:
This branch is metadata-only. I also verified that merging this shared branch before the other split branches avoids duplicated lib/opt_type.py diffs.

[guosran]

Concrete example:
Before this shared PR, each const-op PR had to repeat the same lib/opt_type.py diff.

After this PR:

shared opcode PR
|
+-- #299 DivRTL uses OPT_REM_CONST
+-- #305 CompRTL uses const comparison opcodes
+-- GrantRTL uses OPT_GRT_ONCE_CONST
+-- ShifterRTL uses OPT_LLS_CONST
+-- ConstQueueDynamicRTL tracks const-op consumption

This keeps RTL PRs focused on one module each.