Improve BinOp comparison funcs in operator

[AlexWaygood]

This is a third attempt to give more type specificity to the binary comparison functions in operator, after failed attempts in #6449 and #6448.

This attempt gives no more specificity to the return type of these functions (sadly), but does help constrain the types of the parameters. Currently, the following snippet of code passes mypy, but fails at runtime:

lt(object(), 6)

With this PR, mypy correctly rejects this.

Snippets like the following still continue to raise no errors, however:

lt('foo', 6)

[AlexWaygood]

It might be preferable for type-checkers to special-case these functions, at the end of the day. mypy's clever enough to know that "foo" < 6 should raise an error; it should probably be clever enough to know that the same logic should apply to lt("foo", 6). Interested to hear what others think, however.

^Type-checkers might have difficulty special-casing these functions, because they might well run into the same false-positives I did in #6448

[AlexWaygood]

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

I believe these may all be true positives now?

[github-actions]

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

pandas (https://github.com/pandas-dev/pandas)
+ pandas/core/indexes/base.py:3854: error: Argument 1 has incompatible type "Union[ExtensionArray, ndarray[Any, Any]]"; expected "Union[_SupportsLE, _SupportsGE, _SupportsGT, _SupportsLT]"  [arg-type]
+ pandas/core/indexes/base.py:3854: error: Argument 2 has incompatible type "Union[ExtensionArray, ndarray[Any, Any]]"; expected "Union[_SupportsLE, _SupportsGE, _SupportsGT, _SupportsLT]"  [arg-type]
+ pandas/io/formats/style.py:3502: error: Argument 2 to "ge" has incompatible type "Union[str, Any, float, Period, Timestamp, Timedelta, Sequence[Any], ndarray[Any, Any], NDFrame]"; expected "Union[_SupportsLE, _SupportsGE, _SupportsGT, _SupportsLT]"  [arg-type]
+ pandas/io/formats/style.py:3507: error: Argument 2 to "le" has incompatible type "Union[str, Any, float, Period, Timestamp, Timedelta, Sequence[Any], ndarray[Any, Any], NDFrame]"; expected "Union[_SupportsLE, _SupportsGE, _SupportsGT, _SupportsLT]"  [arg-type]