Apply TypeVar defaults to callables (PEP 696)

[cdce8p]

Implement type application for callables with TypeVar defaults.
Similar to previous PRs, support for TypeVarTuples is still TODO.

Ref: #14851

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

ibis (https://github.com/ibis-project/ibis)
- ibis/expr/operations/tests/test_generic.py:56: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:62: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:65: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:66: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:67: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:69: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:73: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:75: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:79: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:85: error: Type application has too few types (2 expected)  [misc]
- ibis/expr/operations/tests/test_generic.py:88: error: Type application has too few types (2 expected)  [misc]