refactor(java): unify serializer write/read APIs and remove xwrite/xread

[chaokunyang]

Why?

• The Java serializer stack had two parallel APIs (write/read and xwrite/xread) with duplicated logic and branching.
• That duplication increased maintenance cost and made behavior alignment between native Java and xlang paths harder.

What does this PR do?

• Unifies serializer APIs around write/read and removes xwrite/xread call paths across Fory and serializers.
• Refactors Fory read/write flows to dispatch by mode internally (Java vs cross-language) while keeping shared fast paths for primitive types.
• Removes legacy SerializationBinding indirection in serializer and serializer/collection packages and switches call sites to direct serializer/ref-mode APIs.
• Consolidates string serialization method usage (writeString/readString) and updates MemoryBufferObjectInput/Output and serializer call sites.
• Updates GraalVM native-image metadata to drop deleted binding classes and updates affected Java/xlang tests accordingly.

Related issues

Closes #3399
#1017

Does this PR introduce any user-facing change?

• Yes. Custom serializers should use write/read; xwrite/xread-based implementations are removed.
• Does this PR introduce any public API change?
• Does this PR introduce any binary protocol compatibility change?

Benchmark

N/A (refactor-focused PR).