New collection methods for 6.0

[SethDusek]

Add Coll.reverse, startsWith, endsWith. Distinct was removed because of the issue discovered in ergoplatform/sigmastate-interpreter#1051

[coveralls]

Pull Request Test Coverage Report for Build 12858325371

Details

• 66 of 104 (63.46%) changed or added relevant lines in 4 files are covered.
• 11 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.2%) to 78.413%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ergotree-interpreter/src/eval/scoll.rs	18	34	52.94%
ergotree-ir/src/mir/value.rs	10	32	31.25%

Files with Coverage Reduction	New Missed Lines	%
ergo-merkle-tree/src/merkletree.rs	2	95.69%
ergo-merkle-tree/src/batchmerkleproof.rs	3	90.48%
ergotree-ir/src/serialization/types.rs	6	81.82%

Totals
Change from base Build 12853076213:	-0.2%
Covered Lines:	11177
Relevant Lines:	14254

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💛 - Coveralls