THRIFT-6075: Simplify generated Equal code and reduce its runtime cost

Client: delphi

Three changes to generate_equal_container, none of which alter the
comparison semantics:

1. Capture operands into locals: the recursion previously passed
   composed access-path strings down, so expressions like
   Self.List_field[_i][_k][_k2] (property getter + GetItem + two hash
   lookups) were re-evaluated at every mention, up to ~8x per loop
   iteration in deeply nested containers. Operands are now captured
   into fresh locals once per level (already_local skips the copy where
   the operand is a loop variable, pair field or snapshot array slot).

2. Compare maps via pair enumeration and TryGetValue: the scalar-key
   path iterates lhs pairs and fetches the rhs value with a single
   lookup (was three: ContainsKey + lhs[k] + rhs[k], plus repeated
   getters). The non-scalar-key consume-scan snapshots rhs keys and
   values into parallel arrays, removing hash lookups from that path
   entirely.

3. Exit(False) directly on mismatch: a new exit_on_fail mode lets
   field-level, list-element and scalar-key-map comparisons leave the
   generated function immediately instead of threading _eq flags and
   break statements through every nesting level. The flag-and-fall-
   through form remains only for the candidate probes inside the
   set/map consume-scans, where a mismatch means "try the next
   candidate" rather than "structs differ".

Verified by rebuilding the compiler and regenerating ThriftTest,
DebugProtoTest and SimpleException in default, com_types and rtti
modes: all 358 generated Equal/Equals functions are begin/end-balanced,
structs without containers/binaries generate byte-identical code, and
the duplicate-element consume-scan regression shape is preserved.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Jens-G