WIP: Use rangefunc instead of a Manager

[earthboundkid]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 17329642108

Details

• 111 of 116 (95.69%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.8%) to 98.188%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
manager.go	67	72	93.06%

Totals
Change from base Build 9405835144:	-1.8%
Covered Lines:	271
Relevant Lines:	276

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💛 - Coveralls

[earthboundkid]

This has been stalled for a while. I think I need to take a new approach to have something really simple and powerful.

So one, I should probably have a chans package a la #67205 that converts to and from iterators.

Two, a result type that has input, output, error, and a hidden panic field.

Three, simple helpers for Each/All/Map/Race.

Four, a manager that takes an iter of Input and returns various iters of Output or Output plus error, etc.