[PoC] Simplify rule evaluation

[Anilm3]

This change aims to reduce the number of rules that are evaluated on every call to ddwaf_run. Currently the following changes have been done:

• Replace collections with a multiset ordered depending on rule priority (actions, user vs base, type).
• Remove disabled rules from ruleset.
• Select relevant rules based on available targets.

Remaining:

• Replace collections tests.
• Reinstate ruleset test.
• Add other tests.

Note that this is an experimental effort which might lead to a different implementation later on.

[codecov-commenter]

Codecov Report

Merging #218 (dff59da) into master (28d106d) will increase coverage by 0.25%.
The diff coverage is 86.55%.

@@            Coverage Diff             @@
##           master     #218      +/-   ##
==========================================
+ Coverage   82.43%   82.69%   +0.25%     
==========================================
  Files         106      104       -2     
  Lines        4003     4021      +18     
  Branches     1823     1818       -5     
==========================================
+ Hits         3300     3325      +25     
- Misses        281      282       +1     
+ Partials      422      414       -8     

Flag	Coverage Δ
waf_test_none	82.57% <86.55%> (+0.25%)	⬆️
waf_test_sse2	82.65% <86.55%> (+0.25%)	⬆️

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

Files	Coverage Δ
src/context.hpp	88.46% <ø> (+0.96%)	⬆️
src/context_allocator.hpp	73.91% <ø> (ø)
src/indexer.hpp	96.15% <100.00%> (+1.41%)	⬆️
src/mkmap.hpp	68.33% <100.00%> (+1.66%)	⬆️
src/object_store.hpp	85.71% <100.00%> (+2.38%)	⬆️
src/parser/parser_v1.cpp	64.35% <100.00%> (ø)
src/expression.hpp	82.05% <80.00%> (-0.31%)	⬇️
src/rule.hpp	90.47% <95.65%> (+6.47%)	⬆️
src/ruleset_builder.cpp	80.61% <80.00%> (-0.21%)	⬇️
src/ruleset.hpp	73.52% <50.00%> (+9.42%)	⬆️
... and 1 more

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