[Decompiler] More progress on method stuff

[water111]

There's an issue where we can pop things more than once, and this allows stuff to escape ordering.

The best solution is to have the popping functions return a register with a flag that says this was popped and cannot be popped again.

It's possible we have some other code that relies on this double popping, and possibly in a way that's okay. For example, stuff in a temporary stack as part of a condition may be lifted out of the condition, and then can be popped. But this needs to be done more carefully than we are doing now. Either way, this needs to be rethought a little bit.

For example see ExprMethod14DeadPoolHeap, it nests method calls that shouldn't be nested.

I should also see why the side effect check doesn't catch this.

[coveralls]

Pull Request Test Coverage Report for Build 569112032

• 141 of 147 (95.92%) changed or added relevant lines in 4 files are covered.
• 7 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.2%) to 68.546%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
decompiler/IR2/FormStack.cpp	13	14	92.86%
decompiler/IR2/FormExpressionAnalysis.cpp	77	82	93.9%

Files with Coverage Reduction	New Missed Lines	%
decompiler/IR2/FormStack.cpp	1	77.54%
decompiler/analysis/cfg_builder.cpp	2	82.97%
decompiler/IR2/FormExpressionAnalysis.cpp	4	83.74%

Totals
Change from base Build 566935005:	0.2%
Covered Lines:	29065
Relevant Lines:	42402

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💛 - Coveralls