Revert "revert adding std.event.Loop.runDetached"
Revert "revert adding std.event.Loop.runDetached"

This reverts commit 70f37679035e64bacfc4807709da37bc02fbb346.

After discussion, I can see the value provided here, specifically with
avoiding the footgun of defer { suspend { free(@frame()); } }.

However the doc comments are updated to explain the semantics directly,
rather than basing them on the behavior of another programming language.

zig-lang/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,raulgrell/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,andrewrk/zig,andrewrk/zig