Npgsql parameter rewrite

There are two parameter models in Npgsql - ordinal and nominal; we use nominal, but the ordinal API is much more efficient; we could ingest nominal const sql and rewrite it as ordinal

this should include splitting semi-colon multi-statements into DbBatch when possible

tasks:

• basic generalized SQL parser
• SQL syntax tests for postgresql peculiarities
• basic exploration of batch concept
• "real" batch concept (UnifiedBatch, should work with/without DbBatch API)
• codegen (including turn-off-and-onable)
• benchmark:
  • vanilla Dapper, parameterized single batch (Npgsql param rewrite)
  • vanilla Dapper, parameterized multi-batch (Npgsql param rewrite+split)
  • AOT Dapper, rewrite enabled, parameterized single batch, DbBatch disabled
  • AOT Dapper, rewrite enabled, parameterized multi batch, DbBatch disabled
  • AOT Dapper, rewrite enabled, parameterized single batch, DbBatch enabled
  • AOT Dapper, rewrite enabled, parameterized multi batch, DbBatch enabled
• use parser in place of the regex in the regular code path? as an option with fallback?
• docs
• performance tuning of parser (I have a plan, don't ask; kind of a rewrite of the parser) (note this is not critical path)

Start by reviewing the completed generalized SQL parser and UnifiedBatch work described in the issue, then inspect the remaining codegen, benchmark, parser integration, performance, and documentation tasks. Done means the selected remaining scope is implemented and its relevant benchmark or test coverage demonstrates nominal parameters can be rewritten to ordinal parameters, with multi-statements split into DbBatch when supported.