celltypes: compile-time lookup tables for internal cells

[widlarizer]

Intends to fix #5509. The core idea is that CellTypes usage for Yosys internal cells can be directed to a simple compile time constructed integer lookup table for the type IdString index instead of hashing the type. Also improves memory locality with data spread across multiple arrays rather than vector of struct CellTypes.

So far, I've already seen 0-2% gain in the current partial implementation, which only for known_cells and only for CellTypes that only touch internal cells. I'm pretty sure internal cells can be fast pathed to this in CellTypes constructed from user designs, too. Compilation times seem fine so far

• Add unit test that comprehensively checks equivalence with old celltypes

[widlarizer]

opt_expr is like 2.5 faster now leading to 8-10% faster jpeg synth without even excluding abc, wowie

[widlarizer]

I hope everybody is excited to have 40+ second link times with LTO on though!

[widlarizer]

Up to a 16% speedup now, probably mostly thanks to opt_dff by porting ModWalker

[whitequark]

Laughs in 15 minute Wasm LTO link times

[widlarizer]

Sounds like this change would make the LTO link time for WASI even worse. If I rewrite this into a C++ code generator, we should suffer less with LTO across platforms... annoying, but easy