Issue 14543 std.algorithm.searching.until does not handle range sentinels nicely

[jamesragray]

Implemented: https://issues.dlang.org/show_bug.cgi?id=14543
This is somewhere between a bug fix and a new feature because you could argue the old behaviour is wrong.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	14543	normal	std.algorithm.searching.until does not handle range sentinels nicely

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8568"

[thewilsonator]

BTW if you think this PR fixes the issue, make sure the title of (one of) the commit's message starts with Fix issue 14543: followed by the title of the issue.

[pbackus]

Might be worth submitting a draft PR that just changes OpenRight.no to include the full sentinel, and see if any of the projects tested on Buildkite break. If we can get away with it, that would be a much cleaner solution.

cc @atilaneves, this introduces a new public symbol.

[jamesragray]

I have done that here: #8570

[jamesragray]

The problem has been fixed here #8570