CLDR-17014 Use singleton to avoid synchronized in ExtraPaths

[btangmu]

CLDR-17014

• This PR completes the ticket.

ALLOW_MANY_COMMITS=true

[macchiati]

Almost there, thanks!

[macchiati]

At the end of this method, you need to make paths be an ImmutableSet. Add an extra parameter to addPaths, etc. and change this to:

Suggested change

	paths = new HashSet<>();
	addPaths(NameType.SCRIPT);
	addPaths(NameType.LANGUAGE);
	Set<String> temp = new TreeSet(); // might as well put them in order; easier to debug
	addPaths(NameType.SCRIPT, temp);
	addPaths(NameType.LANGUAGE, temp);
	paths = ImmutableSet.copyOf(temp); // preserves order (Sets.copyOf doesn't)

[btangmu]

@macchiati the 2nd commit makes paths an ordered ImmutableSet as you suggested

[macchiati]

It would be slightly better to add pathsTemp as a parameter to addPaths, but this works and only costs a trifling bit of memory.

[btangmu]

It would be slightly better to add pathsTemp as a parameter to addPaths, but this works and only costs a trifling bit of memory.

Making it a parameter might reduce the data size by a few bytes, but increase the code size by a slightly larger number of bytes, since addPaths and addAltPath have dozens of callers. Anyway, this can be revisited in follow-up refactoring when moving more code from CLDRFile to ExtraPaths.

[macchiati]

good point!