Lazy default for Option.getOrElse/Coll.getOrElse

[SethDusek]

Add lazy default for getOrElse and Coll.get, also transpose Box<Option> so Option<Box> to make pattern-matching simpler and avoid allocating for None
For #787

[coveralls]

Pull Request Test Coverage Report for Build 12611199821

Details

• 38 of 48 (79.17%) changed or added relevant lines in 11 files are covered.
• 10 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.008%) to 78.453%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ergotree-interpreter/src/eval/coll_by_index.rs	6	7	85.71%
ergotree-interpreter/src/eval/extract_reg_as.rs	1	2	50.0%
ergotree-interpreter/src/eval/option_get.rs	1	2	50.0%
ergotree-interpreter/src/eval/sbox.rs	1	2	50.0%
ergotree-ir/src/mir/value.rs	4	5	80.0%
ergotree-ir/src/mir/constant.rs	2	7	28.57%

Files with Coverage Reduction	New Missed Lines	%
ergotree-ir/src/serialization/types.rs	10	80.42%

Totals
Change from base Build 12589822362:	-0.008%
Covered Lines:	11076
Relevant Lines:	14118

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💛 - Coveralls