std.ArrayHashMap: add unstable sorting capability

[andrewrk]

These functions are available:

zig/lib/std/array_hash_map.zig

Lines 1229 to 1243 in d68f39b

	/// Sorts the entries and then rebuilds the index.
	/// `sort_ctx` must have this method:
	/// `fn lessThan(ctx: @TypeOf(ctx), a_index: usize, b_index: usize) bool`
	pub inline fn sort(self: *Self, sort_ctx: anytype) void {
	if (@sizeOf(ByIndexContext) != 0)
	@compileError("Cannot infer context " ++ @typeName(Context) ++ ", call sortContext instead.");
	return self.sortContext(sort_ctx, undefined);
	}
	pub fn sortContext(self: *Self, sort_ctx: anytype, ctx: Context) void {
	self.entries.sort(sort_ctx);
	const header = self.index_header orelse return;
	header.reset();
	self.insertAllEntriesIntoNewHeader(if (store_hash) {} else ctx, header);
	}

However, unstable sort is preferred when possible. This API should offer unstable sorting as well.