Implemented budgets

[DurieuxPol]

Added budgets to represent a cost that an execution of MuTalk cannot exceed.
Currently there are MutationTestingFreeBudget, which is essentially a budget with no constraint and do the same as before, without budgets, and MutationTestingTimeBudget, which restrict the execution time with a time constraint.

In my implementation, the beggining of the timer is at the start of the run method rather than before the generateResults, so it takes into account the time to run the tests a first time before evaluating the tests with the mutants.

Also, if the time constraint is exceeded while the tests are running against a mutant, the execution continues until all tests have finished, then the constraint blocks the next mutants from being evaluated.

An example of use:

[coveralls]

Pull Request Test Coverage Report for Build 7143029780

• 190 of 297 (63.97%) changed or added relevant lines in 11 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 60.395%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/MuTalk-Model/MutationTestingBudget.class.st	4	8	50.0%
src/MuTalk-TestResources/AuxiliarClassForMutationTestingBudget.class.st	0	4	0.0%
src/MuTalk-Model/ManualMutatedMethodSelectionStrategy.class.st	0	8	0.0%
src/MuTalk-Model/MutationTestingAnalysis.class.st	60	151	39.74%

Totals
Change from base Build 7083678478:	0.1%
Covered Lines:	3945
Relevant Lines:	6532

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💛 - Coveralls

[DurieuxPol]

The time budget tests pass for me, but they seemingly fail in the CI. I'm going to change them and see.

[guillep]

Interesting, the tests pass in Pharo11 but not in Pharo10.

@DurieuxPol could you test in Pharo10?

Also, maybe later we should

• evaluate if we keep supporting Pharo9
• add CI support for Pharo12