[lib] Non-member swap inconsistently specified in class synopsis

[JohelEGP]

In header synopsis only	In class synopsis
pair, tuple, optional, variant, any
{unique,shared}_ptr	weak_ptr
	function
array, stack	deque, forward_list, list, vector-not-of-bool, (multi){map,set}, unordered_(multi){map,set}, (priority_)queue
valarray
	basic_{stringbuf,(i,o)stringstream,filebuf,(i,o)fstream,syncbuf} (only)
fs::path
basic_regex, match_results
thread
	{unique,shared}_lock
	promise, packaged_task

The remaining are friends or depend on the generic std::swap via ADL.

[JohelEGP]

Considering #4037 (comment) and #4035 (comment), does this still need the decision-required tag?

[jensmaurer]

Summary of editorial meeting consensus documented in #4035 and #4037: non-member swap should be in the header synopsis, not in the class synopsis.