Log Message:
mu: update to 1.12.9

- new command mu4e-analyze-last-query
- update to bookmarking
- experimental: a "transient" menu, which provides easy access to
  some common (and some not so common) functions in mu4e (requires
  emacs >=28)
- The mu server uses PCRE-compatible regexps (for addresses), which
  are not necessarily compatible with Emacs regular expressions.
  However, mu4e can now automatically translate; this depends on the
  pcre2el package which the user should install when using regular
  expression-addresses.

- the cleanup phase after indexing has been sped up significantly
- updated documentation; man-pages and mu4e reference manual