Fix locations in presence of nested trivia, take 2

[povik]

Follow-up from #1035

I gave up on making the change to eradicate nested trivia, instead I made effort to make the explicit locations on trivia consistently defined.

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.77%. Comparing base (8174a94) to head (fe6b1bb).
Report is 28 commits behind head on master.

Files with missing lines	Patch %	Lines
source/parsing/Token.cpp	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1136      +/-   ##
==========================================
+ Coverage   94.76%   94.77%   +0.01%     
==========================================
  Files         191      191              
  Lines       47716    47803      +87     
==========================================
+ Hits        45217    45305      +88     
+ Misses       2499     2498       -1     

Files with missing lines	Coverage Δ
include/slang/parsing/Token.h	100.00% <ø> (ø)
source/parsing/Preprocessor.cpp	100.00% <100.00%> (ø)
source/parsing/Token.cpp	93.31% <92.85%> (-0.15%)	⬇️

... and 23 files with indirect coverage changes

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