[blotus]

tx.GetField() calls col.FindAll() for every rule × every variable it targets. Each call builds a
fresh []corazarules.MatchData + []types.MatchData holding every entry of the collection:

• Map.FindAll / NamedCollectionNames.FindAll: two allocations of size n per call.
• ConcatKeyed.FindAll / ConcatCollection.FindAll (ARGS = ARGS_GET + ARGS_POST, ARGS_NAMES, …):
  calls the children's FindAll, rewrites Variable_ on the results in place (replaceVariable),
  and grows the result with repeated append.

Within a phase the collections don't change, so this is the same copy rebuilt hundreds of times.
Cost is O(rules × args): with CRS, a 16KB JSON body (~600 ARGS) allocated ~20MB per request, and
madvise + memclr + GC were ~40–50% of CPU.

GetField also lowercases every match's key (strings.ToLower(c.Key())) even when the rule has no
exceptions, and compacts the slice in place.