Add QPACK dynamic table support

[SC123667]

Resolves #225

Summary

• add a capacity-bounded FIFO QPACK dynamic table with reference-safe eviction
• implement encoder and decoder stream instructions plus every dynamic field-line representation
• integrate acknowledgments, cancellations, blocked-section resumption, and flow-controlled instruction queues into HTTP/3
• use a conservative encoder policy that references only acknowledged entries to avoid creating blocked streams
• harden 62-bit prefixed-integer decoding and dynamic-index bounds

Testing

• cargo fmt --all -- --check
• git diff --check
• cargo test
• cargo clippy --all -- -D warnings
• cargo clippy --all -F ffi -- -D warnings
• cargo build --all --no-default-features -F h3

The tests cover RFC 9204 Appendix B, dynamic-table reuse and eviction, incremental instructions, post-Base references, blocked field-section resumption, low encoder-stream flow-control credit, sensitive fields, and malformed integer/capacity inputs.