Refactoring of auth-source-pass

Refactoring of auth-source-pass

* lisp/auth-source-pass.el (auth-source-pass--find-match): Refactor by
moving some code to auth-source-pass--disambiguate.
(auth-source-pass--disambiguate)
(auth-source-pass--entries-matching-suffix): New function.
(auth-source-pass--find-match-unambiguous)
(auth-source-pass--select-from-entries)
(auth-source-pass--entry-reducer): Refactor to simplify and improve
logging.
(auth-source-pass--matching-entries)
(auth-source-pass--accumulate-matches): Remove.
* test/lisp/auth-source-pass-tests.el: Complete rewrite to facilitate
maintenance.
(auth-source-pass--have-message-containing): Remove.
(auth-source-pass--have-message-matching)
(auth-source-pass--explain--have-message-matching)
(auth-source-pass--explain-match-entry-p)
(auth-source-pass--includes-sorted-entries)
(auth-source-pass--explain-includes-sorted-entries)
(auth-source-pass--explain-match-any-entry-p)
(auth-source-pass--matching-entries)
(auth-source-pass-match-entry-p)
(auth-source-pass-match-any-entry-p): New function.