Conservatively fold matcher-like builtins in EvaluateBuiltins

[dancewithheart]

Fixes #6167 by

• Detect matcher-like builtins via biMatcherLike
• Allow folding only when all branches are value-like
• Otherwise, leave the term unchanged

This preserves existing optimizations (e.g. ifThenElse True 1 2) while avoiding the unsound case e.g. when the discarded branch fails:

[ { (builtin ifThenElse) (con integer) }
    (con bool True)
    (con integer 1)
    [ [ (builtin divideInteger) (con integer 1) ] (con integer 0) ]
]

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