Harden TiDB distributed catalog management

[ngaut]

Summary

• retry TiDB catalog-management transactions on documented whole-transaction retry errors
• move TransactWriteItems idempotency fully to the TiDB data database and drop the unused catalog table
• update TiDB docs/requirements for distributed management, native TTL, and data-owned idempotency

Verification

• cargo fmt --all
• cargo test -j12 -p extenddb-storage-tidb
• cargo clippy -j12 -p extenddb-storage-tidb --all-targets -- -D warnings
• cargo test -j12 -p extenddb --no-default-features --features tidb --all-targets
• cargo clippy -j12 -p extenddb --no-default-features --features tidb --all-targets -- -D warnings
• docs/build-docs.py
• live TiDB playground migration check: catalog reached 0.0.12, catalog idempotency table absent, data idempotency table present with native TTL
• git diff --check

Notes

• Does not touch the PostgreSQL module.
• This is a new PR from ngaut/extenddb and does not modify Add TiDB storage backend ExtendDB/extenddb#140.