fix(generation): fp4 byte-size and stale v1→v2 MLA warning

[Gpgabriel25]

Changes

fp4-safe byte-size calculation

_create_mixed_standard_ragged_page_cache_configs and
_create_mixed_standard_unified_attention_cache_configs both used
jnp.finfo(kvdtype).bits // 8 — the same bug fixed in the caching
layer (see PR #XX). Replaced with jnp.dtype(kvdtype).itemsize so
fp4 / integer KV dtypes work correctly through the generation mixin too.

Correct v1 → v2 in mixed-MLA log warning

The warning that fires when mixed MLA/non-MLA layers are detected was
logging multi_latent_ragged_page_attention_v1 as the target mechanism.
The actual target is v2. Fixed the string literal.

Tests

New: test_esurge_compatible_model_logs_v2_for_mixed_mla — verifies
that both the emitted warning and the resulting attn_mechanism /
decode_attn_mechanism / mla_attn_mechanism kwargs all reference
multi_latent_ragged_page_attention_v2. 1 passed.

[erfanzar]

Hi @Gpgabriel25 and thanks for contributing to easydel

All of ur PRs are solid and good but it will take time to merge them since i want to keep git worktree the same before i merge branch 'vnext'