Fix(memorization) issue 710 py lsp memoization

[LA-10]

What does this PR do?

Fixes #710 index_repository hangs during the definitions pass on Python files with deeply chained method calls, consuming 800+ s and ~1.4 GB with no progress.

py_eval_expr_type (internal/cbm/lsp/py_lsp.c) recursively evaluates expression types with no memoization. Chained calls cause the same sub-chains to be re-evaluated at every level roughly O(2^N) in chain depth

Memoize py_eval_expr_type, keyed by node start byte. Each sub-expression is typed once, collapsing chain evaluation to O(depth). The original body is renamed _uncached and wrapped by a thin memoizing entry results identical, only redundant recomputation removed. Cache is arena-allocated per file (freed automatically).

Added pylsp_issue710_deep_call_chain_no_hang to tests/test_py_lsp.c a ~40-link chain that hangs on the old code and passes on the fix.

Checklist

• Every commit is signed off (git commit -s) — required, CI rejects
  unsigned commits (DCO, see CONTRIBUTING.md)
• Tests pass locally (make -f Makefile.cbm test)
• Lint passes (make -f Makefile.cbm lint-ci)
• New behavior is covered by a test (reproduce-first for bug fixes)

[DeusData]

Huge thanks for opening this PR and for the work you put into it.

The maintainer shop is currently full, so this may sit for a bit before it gets a proper review. We will come back to this as soon as possible with real feedback; I wanted to make sure it did not sit unacknowledged in the meantime.