Fixes #10260

Fixes #10213

The oh-my-zsh-git package sets the cache directory to `$HOME/.cache/oh-my-zsh`, so
Oh My Zsh will be compatible with it.

Fixes #10193

Fixes #10183

Closes #9223

skip the update check at initialization if DISABLE_AUTO_UPDATE is set to true

Closes #8981

If `$SHORT_HOST` contains invalid filename characters, the compinit call doesn't
error, but the zcompdump metadata write does. Use `tee` instead so we can silence
the error.

See https://github.com/ohmyzsh/ohmyzsh/commit/dd1a72696f162fd5285a104b5f63970deb66e8b0#commitcomment-38984764

BSD cmp doesn't have the option of reading from stdin, so use process
substitution instead.

The statements for selecting a random theme in oh-my-zsh.sh and the themes
plugin are duplicate. Most people eventually settle on a theme, making those
lines in oh-my-zsh.sh superfluous. To address those, it may makes sense to put
the random theme functionality into a theme of its own (since themes are just
zsh scripts.

Fixes #8545

Co-authored-by: Se De <Sede7473@gmail.com>

We have to assume that if people disabled the compfix system they really want
their completion to work, ignoring any permission issues.

Fixes #5651
Fixes #5957
Fixes #6461

 - Adding documentation
 - Note the effect empty array
 - Fix spelling
 - Using new test `[[...]]`

Revert "Move custon *.zsh file sourcing up so that they can load plugins and other things that come after."

This reverts commit a28dbc83.

Completion-dependent directories with insecure permissions or ownership (e.g.,
group or other writability) are now detected, reported, and sanitized on OMZ
startup rather than unsafely ignored -- which resulted in effectively empty
completion caches and obscure compdef() errors resembling
"compdef: unknown command or service: git".

This fixes long-standing issues #630, #3356, and #3455 and related Babun issues
159, 281, and 322 -- and probably numerous other duplicates.