Array method definition revamp: Use case collection

We've gotten numerous issue reports and PRs to change the methods of Array, particularly reduce, map, and filter. The built-in test suite doesn't cover these very well, and these methods interact with each other and the surrounding contextual type in fairly subtle ways.

@jablko has done a great job at #33645 collecting a variety of issues into a single PR; we need to augment this PR (or something like this) with a proper test suite so we can be sure about what's being changed.

I'd like to create a clearinghouse issue here to collect self-contained (I CANNOT POSSIBLY STRESS THIS ENOUGH, SELF-CONTAINED, DO NOT IMPORT FROM RXJS OR WHAT HAVE YOU) code samples that make use of the array methods.

Please include with your snippet:

• Compiler settings
• Compiler version you were testing with
• The expected behavior (examples that should and should not produce errors are both useful)
• No imports or exports; snippets need to be self-contained so that we can put them into our test suite without extra complications

Once we've established a critical mass of code snippets, we can start combining the existing PRs into an all-up revamp and assess its impact to real-world code suites to figure out which changes don't result in unacceptable breaking changes.

ｓｅｌｆ－ｃｏｎｔａｉｎｅｄ

Beginne mit der Prüfung der gesammelten Beispiele in Issue #36554 und dem zugehörigen PR #33645, wobei du dich auf die Array-Methoden reduce, map und filter konzentrierst. Füge nur in sich geschlossene Snippets mit Compilereinstellungen, Compilerversion und erwarteten Diagnosen hinzu; die Aufgabe ist abgeschlossen, wenn eine ausreichend breite Testsammlung vorhanden ist, die als Grundlage für die vorgeschlagene Überarbeitung dienen kann.