Add lexer detection of translate_on/off pragmas

[povik]

Follow-up to #1100 with a changed approach. The detection now happens in lexer, not preprocessor. Tests are missing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.63%. Comparing base (f31d20e) to head (7e2329d).
Report is 31 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1157      +/-   ##
==========================================
- Coverage   94.84%   94.63%   -0.21%     
==========================================
  Files         191      195       +4     
  Lines       47944    50261    +2317     
==========================================
+ Hits        45472    47566    +2094     
- Misses       2472     2695     +223     

Files with missing lines	Coverage Δ
include/slang/parsing/Lexer.h	100.00% <ø> (ø)
source/parsing/Lexer.cpp	99.51% <100.00%> (+0.03%)	⬆️

... and 159 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f31d20e...7e2329d. Read the comment docs.

[MikePopoloski]

This approach seems ok. I think there must be a way to optimize it a bit more to avoid going into the full loop to check for cases since 99.9% of comments won't match, but it's probably ok for now.

You do need to add tests though; ideally you get full coverage of all branches, especially for something critical like the lexer.

[povik]

You do need to add tests though; ideally you get full coverage of all branches, especially for something critical like the lexer.

OK, I have started some testing, let me see what the report will say

[povik]

Looks like the coverage is full