1. Escape '%' characters in URLs - only unescaped data
   should be passed to URL helpers

2. Add an `escape_segment` helper to `Router::Utils`
   that escapes '/' characters

3. Use `escape_segment` rather than `escape_fragment`
   in optimized URL generation

4. Use `escape_segment` rather than `escape_path`
   in URL generation

For point 4 there are two exceptions. Firstly, when a route uses wildcard
segments (e.g. *foo) then we use `escape_path` as the value may contain '/'
characters. This means that wildcard routes can't be optimized. Secondly,
if a `:controller` segment is used in the path then this uses `escape_path`
as the controller may be namespaced.

Fixes #14629, #14636 and #14070.

Cherry picked from:
  e2ef83f8
  a6179257
  5460591f

Conflicts:
	actionpack/CHANGELOG.md