Fix keyword-only arg crash, max_iterations=0 NameError, and format_boundargs TypeError

[Dev9269]

Summary

Fixes three crashes:

1. condition_parser._extract_a_and_kw — KEYWORD_ONLY parameters were appended to both positional and keyword args, crashing on re-call for deal contracts. Now handled via \param.kind\ including VAR_KEYWORD/VAR_POSITIONAL.
2. core.analyze_calltree — \max_iterations=0\ raised \NameError: i not defined\ in the iteration-count debug message.
3. util.format_boundargs — unbound VAR_POSITIONAL/VAR_KEYWORD args fell back to \inspect._empty, raising TypeError. Now defaults to ()\ / {}.

Tests

Added: \ est_deal_pre_keyword_only_arg, \ est_max_iterations_zero_does_not_crash, \ est_format_boundargs_without_varargs.
Affected files: 133 passed, 3 skipped.

[pschanely]

@Dev9269 This is lovely - thank you! Would you like to add yourself with a link of your choice to changelog.rst?

[pschanely]

@Dev9269 This is lovely - thank you! Would you like to add yourself with a link of your choice to changelog.rst?

Gonna merge this to get it in, but feel free to open another PR if so!