perf: optimize map validation for common key types

[lyne7-sc]

Which issue does this PR close?

• Closes #.

Rationale for this change

This PR optimizes map key validation for common key types.

Previously, map validation always used the generic ScalarValue::try_from_array path, which is more expensive than necessary for common key types such as primitive integers, strings, and binary values.

What changes are included in this PR?

• specialize map key validation for primitive, string, and binary key types
• keep the generic fallback for unsupported key types

Are these changes tested?

Yes. current unit tests and slts test passed. benchmark added.

Are there any user-facing changes?

No.

[lyne7-sc]

Benchmarks:

group                                                main                                   optimized
-----                                                ----                                   ---------
map_1000_binary                                      11.46    75.1±2.47ms        ? ?/sec    1.00      6.6±0.25ms        ? ?/sec
map_1000_int32                                       7.85     32.4±0.61ms        ? ?/sec    1.00      4.1±0.17ms        ? ?/sec
map_1000_utf8                                        9.63     76.0±2.30ms        ? ?/sec    1.00      7.9±0.28ms        ? ?/sec