fix: stop Set.All iteration when requested

[immanuwell]

Set.All() keeps yielding after a caller stops early.
With 2 values, a normal break panics with range function continued iteration after function for loop body returned false

Repro:

for range part.NewSet("first", "second").All() {
	break
}

Before this panics.
After this fix exits cleanly

The iterator now returns when yield is false, with a regression test

Tested with make test, make test-race, make build and make bench

[joamaki]

Oopsie! Thanks for the fix.