[PoC] Chained evaluation for rules

[Anilm3]

This is a proof-of-concept of chained evaluation, a feature which allows conditions to evaluate the result of previous conditions.

Currently, the following caveats apply:

• Testing is non-exhaustive
• Chained evaluation is not yet supported on exclusion filters
• The code has many compromises due to time constraints, which might translate into bugs
• Some structures and caches might have some duplicates
• Some context-bound structures aren't yet using the context allocator

[codecov-commenter]

Codecov Report

Merging #180 (b98b1a4) into master (4e22824) will decrease coverage by 0.34%.
The diff coverage is 54.76%.

@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
- Coverage   64.09%   63.75%   -0.34%     
==========================================
  Files          98      100       +2     
  Lines        3217     3416     +199     
  Branches     1467     1556      +89     
==========================================
+ Hits         2062     2178     +116     
- Misses        277      298      +21     
- Partials      878      940      +62     

Flag	Coverage Δ
waf_test	63.75% <54.76%> (-0.34%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/condition.hpp	71.42% <ø> (-28.58%)	⬇️
src/iterator.hpp	70.00% <0.00%> (-3.69%)	⬇️
src/parser/specification.hpp	100.00% <ø> (ø)
src/rule.cpp	50.00% <0.00%> (-35.72%)	⬇️
src/ruleset_builder.cpp	47.74% <0.00%> (ø)
src/parser/parser_v1.cpp	23.15% <21.56%> (-2.34%)	⬇️
src/parser/parser_v2.cpp	43.42% <38.46%> (-0.69%)	⬇️
src/expression.cpp	61.84% <61.84%> (ø)
src/expression.hpp	77.35% <77.35%> (ø)
src/condition.cpp	45.28% <100.00%> (-11.33%)	⬇️
... and 1 more

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more