Namespacing: Add MLD_CONFIG_PARAMETER_SET + MLD_CONFIG_NAMESPACE_PREFIX, modify api, common, config accordingly

[jakemas]

Still WORK in progress. Steps for multi-level build.
testing removing mldsa_mode in another CI

• Resolves Config: Add MLD_CONFIG_PARAMETER_SET + MLD_CONFIG_NAMESPACE_PREFIX #446

Core System Changes:

1. Replaced hardcoded namespace prefixes (MLD_44_ref_, MLD_65_ref_, MLD_87_ref_) with configurable MLD_CONFIG_NAMESPACE_PREFIX system
2. Added missing build infrastructure (test/mk/compiler.mk, test/mk/auto.mk) with compiler feature detection and host capability matching
3. Migrated parameter configuration from MLDSA_MODE (2/3/5) to MLD_CONFIG_PARAMETER_SET (44/65/87) with backward compatibility
4. Separated function declarations from api.h to sign.h, leaving only constants in public API
5. Implemented dual namespace macros - MLD_NAMESPACE() for shared functions, MLD_NAMESPACE_K() for parameter-specific functions
6. Fixed native backend integration with proper include order dependencies and platform-specific assembly symbol handling
7. Updated test configuration files (break_pct_config.h, custom_zeroize_config.h) to use new namespace system
8. Updated CBMC proofs/break_pct/custom_zeroize/stack_use: to use new namespace/api.h where needed

Parameter set naming convention

mlkem-native:

• MLK_CONFIG_PARAMETER_SET (512, 768, 1024) → MLKEM_K (2, 3, 4)

mldsa-native:

• MLD_CONFIG_PARAMETER_SET (44, 65, 87) → MLDSA_K (4, 6, 8) and MLDSA_L (4, 5, 7)

or do we want to preserve the NIST levels in some respect?

[jakemas]

hmm looks like mld_polyvec_matrix_expand CBMC is failing on ml-dsa-87

[jakemas]

theory, cant be defined from here, so its defaulting to 65, and breaking in 87 case (as never set)