Enhance Piracy detection by considering more methods

[lgoettgens]

Resolves #155 and resolves #157.

The main change is a re-implementation of all_methods. Unfortunately, the old data source names(MyModule) was missing some callables (#157) and methods of non-imported functions that have been defined in a fully qualified way (#155). The proposed implementation works very similarly to Test.detect_ambiguities and Test.detect_unbound_args by iterating over all names of all currently loaded modules, and then filtering out the methods that are indeed defined in MyModule.

I furthermore added some tests displaying the new functionality. The main point here is that

Aqua.jl/test/test_piracy.jl

Lines 58 to 62 in 94a9c7a

	# Assign them names in this module so they can be found by all_methods
	a = Base.findfirst
	b = Base.findlast
	c = Base.findmax
	d = Base.findmin

is no longer needed.

[codecov]

Codecov Report

Merging #156 (9ae3c19) into master (5db17b8) will decrease coverage by 9.94%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #156      +/-   ##
==========================================
- Coverage   77.07%   67.13%   -9.94%     
==========================================
  Files          11       11              
  Lines         724      569     -155     
==========================================
- Hits          558      382     -176     
- Misses        166      187      +21     

Flag	Coverage Δ
unittests	67.13% <100.00%> (-9.94%)	⬇️

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Impacted Files	Coverage Δ
src/piracy.jl	90.16% <100.00%> (-0.89%)	⬇️

... and 10 files with indirect coverage changes

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[lgoettgens]

Ping @fingolfin

[fingolfin]

I have no idea what this does exactly but I trust you thought this through.