Fix error message for incorrect calls with unlock_instance

[nikfilippas]

While reviewing baryons_v3 I realized I had not implemented a fallback mechanism in case the input of unlock_instance was nonsense. This resulted to a very cryptic error message when

• users called the decorated function with wrong arguments
• developers specified an incorrect number in argv

@ccl.unlock_instance(argv=1)
def func(item, pk, a0=0, *, a1=None, a2):
    return

func()  # wrong call to function

Traceback (most recent call last):

  Cell In[3], line 1
    func()

  File ~/CCL/pyccl/base.py:419 in wrapper
    arg = args[argv] if size > argv else list(kwargs.values())[argv-size]  # noqa

IndexError: list index out of range

This PR uses inspect.signature.bind which mimics the default Python behavior for incorrect function calls. The main difference with what is currently in master is that we now have to specify the name of the unlocked argument, rather than the argv. As an added bonus, it checks on import if the name actually exists, or if the developer has made a typo. The previous version would only complain at runtime.

[coveralls]

Pull Request Test Coverage Report for Build 4492834264

• 12 of 12 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 97.859%

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Totals
Change from base Build 4477013263:	0.002%
Covered Lines:	5484
Relevant Lines:	5604

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💛 - Coveralls