Add a C# language LSP resolver mirroring the existing Go/C/PHP/Python
modules: type evaluation, using-directive resolution, method lookup,
and a corpus-seeded .NET BCL stdlib data table.
- internal/cbm/lsp/cs_lsp.{c,h}: resolver implementation
- internal/cbm/lsp/generated/cs_stdlib_data.c: BCL type/method tables
- wire CBM_LANG_CSHARP dispatch in cbm.c and lsp_all.c
- register cs_lsp + cs_lsp_bench suites in the test harness
- tests/test_cs_lsp.c, tests/test_cs_lsp_bench.c
(cherry picked from commit 8f677c67a0c9d7829cd6ac27393de2d0aaaac534)