Fix getobj for parameterized callable objects

[lgoettgens]

Fixes #49 and fixes #141.

The main change is the unwrapping of UnionAlls in getobj. While looking through it, I furthermore used it in the piracy tests as well (where until now the function was basically inlined). And in getobj the deprecated function tuple_type_head was used, the alternative is fieldtype(-, 1). Both changes have been tested in julia 1.0, 1.6 and 1.9.

The MWE in #49 (comment) by @mtsch for julia 1.0 (Aqua.test_ambiguities([MWE, Base, Core], exclude=[convert])) reports precisely the same 52 ambiguities (up to order) as with the current master, but there are no errors.

The much smaller MWE in #49 (comment) by @fingolfin for julia 1.9 no longer fails.

Please check if this fixes it for you as well.

[lgoettgens]

I will try to construct a test for this without introducing an external test dependency.

[codecov]

Codecov Report

Merging #142 (b18fd2e) into master (03b678b) will increase coverage by 11.08%.
The diff coverage is n/a.

❗ Current head b18fd2e differs from pull request most recent head ca16eb8. Consider uploading reports for the commit ca16eb8 to get more accurate results

@@             Coverage Diff             @@
##           master     #142       +/-   ##
===========================================
+ Coverage   65.69%   76.78%   +11.08%     
===========================================
  Files          11       11               
  Lines         548      715      +167     
===========================================
+ Hits          360      549      +189     
+ Misses        188      166       -22     

Flag	Coverage Δ
unittests	76.78% <ø> (+11.08%)	⬆️

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[lgoettgens]

For the added testcase in the style of the method erroring #49 (comment), one can now see the error in the CI logs (e.g. https://github.com/JuliaTesting/Aqua.jl/actions/runs/5313233395/jobs/9618834173?pr=142#step:4:139). Unfortunately, due to the implementation of test_ambiguities, we are not able to test for their absence. I'll try to circumvent that somehow.

[fingolfin]

Looks good to me, thanks!