fix: fix callback of throttled/debounced decorated functions with mismatched args

[tlambert03]

similar to #183, this fixes calling a qdebounced/qthrottled function with too many arguments

class Emitter(QObject):
    sig = Signal(int, int, int)

@qdebounced
def func(a: int, b: int):
    ...

obj = Emitter()
obj.sig.connect(func)
obj.sig.emit(1, 2, 3)  # currently breaks, too many args

I had to do it manually here (meaning pass func(*args[:max_args])), because of a bug in pyside that prevents proper inspection of callable objects:
https://bugreports.qt.io/browse/PYSIDE-2423

This PR also changes the decorator pattern to return an instance of ThrottledCallable (whereas before it just returned an object that implemented the protocol). I think it makes for a much clearer read

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.76% ⚠️

Comparison is base (41ea4e8) 86.05% compared to head (aac1d14) 85.29%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #184      +/-   ##
==========================================
- Coverage   86.05%   85.29%   -0.76%     
==========================================
  Files          36       36              
  Lines        2746     2747       +1     
==========================================
- Hits         2363     2343      -20     
- Misses        383      404      +21     

Files Changed	Coverage Δ
src/superqt/utils/_throttler.py	89.62% <100.00%> (+0.40%)	⬆️

... and 9 files with indirect coverage changes

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