New type parameter syntax: parameters should be broken up before type parameters

Describe the style change

In functions with the new type parameter syntax, the type parameter bracket should only be made multi-line if it itself does not fit on one line. (Sorry, this is best explained with an example; see below.)

Examples in the current Black style

def f[
    T
](a_long_param_name: list[T] | tuple[T, ...], another_long_param_name: T) -> list[T]:
    pass

def g[
    T
](
    a_long_param_name: list[T] | tuple[T, ...],
    another_long_param_name: T,
    a_boolean_flag: bool,
) -> list[T]:
    pass

Desired style

def f[T](
    a_long_param_name: list[T] | tuple[T, ...], another_long_param_name: T
) -> list[T]:
    pass

def g[T](
    a_long_param_name: list[T] | tuple[T, ...],
    another_long_param_name: T,
    a_boolean_flag: bool,
) -> list[T]:
    pass

Additional context

Tested on latest commit: https://github.com/psf/black/commit/e1036119f264a846bb049fad8404df318bc2f455

Start by reproducing the two Python examples from the issue with Black and trace the formatter entry point that handles function definitions with type parameters. The change is done when the examples match the desired style without changing unrelated formatting, and the relevant formatting checks pass.