gh-126850: Handle multiple functions with same name in StatsProfile

[ejthomas]

Adds a new attribute func_profile_by_loc to the StatsProfile class in pstats.py that provides access to the function profiles keyed by a tuple of filename, linenumber and function name (rather than just function name as used in func_profiles), so that profiling data for multiple functions with the same name can be accessed via the StatsProfile data structure.

A new test is added to highlight the new behaviour in test_pstats.py.

A new attribute is used instead of changing the existing behavior for backwards compatibility (though I'm aware this is very similar to the existing attribute, I think this edge case not handled in func_profiles is relatively common when profiling more complex code where certain common names like run() or build() are likely to appear multiple times).

I considered making the key a more formal data structure with named attributes like a frozen dataclass or namedtuple, but when looking at the surrounding code, it looked like a simple tuple was a good fit. I gave it an alias to clarify intent, but I'd be very happy to use an alternative approach if that would improve readability further.

• Issue: pstats.Stats.get_stats_profile can't handle functions with the same name #126850

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