Select random probability

[jim22k]

NOTE: Major overhaul of graphblas.select

• Passing multiple selectors is no longer allowed This greatly simplifies the implementation as we don't need to line up thunks with selectors.

• New selector: "probability"

  • This takes a thunk in range 0-1 determining the probability of selecting each value
  • A choose_uniform context is required to be passed as well, similar to our other random operations

Also Note: The test for this functionality is in test_select_probability.mlir and uses the new functional test goodness, allowing us to actually run a test that exercises the C++ random functions. We should look to replace all the lower_xxx.mlir tests with functional tests in the future.

[coveralls]

Pull Request Test Coverage Report for Build 1408596611

• 16 of 22 (72.73%) changed or added relevant lines in 3 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 82.809%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
mlir_graphblas/ops.py	10	16	62.5%
<!--	Total:	16	22	72.73%	-->

Files with Coverage Reduction	New Missed Lines	%
mlir_graphblas/src/build.py	2	89.19%
<!--	Total:	2		-->

Totals
Change from base Build 1399803456:	0.1%
Covered Lines:	3425
Relevant Lines:	4136

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💛 - Coveralls