Rework codegen code

[pathscale]

For now really huge amount of logic is generated via codegen with worktable! procedural macro. This leads to debug issues as it's hard to debug generated code.

Main solution is to rework main WorkTable object and move as much as possible from codegen part to src.

It should be possible to do with proper abstractions over worktable's inner structures.

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Migrated from pathscale/wt-dead#128. Originally opened by @Handy-caT on 2026-01-08T20:56:25Z.

[pathscale]

PR #46 does not resolve this architectural refactor. There is no honest runtime pass/fail test for the requested ownership shift; current codegen/src remains about 16,461 Rust LOC versus about 14,402 under src, and generated table/query implementations remain in the macro crate. Skipping a synthetic test and retaining this as post-1.0 work.