Fixes #8676

Provides a different solution to #8332 and #8333

Add random theme and consolidate logic from init and themes plugin

Co-authored-by: Fran Garcia <fran.miranda@gmail.com>

Also add comments and unset leftover variables, and print only the
name of the theme loaded.

When looking for $ZSH_CUSTOM themes, the chosen algorithm is to add
the theme names to the pool disregarding the path, and then source
whatever theme is selected with the same logic as the init script,
which is to source first custom themes even if there is another
default theme of the same name.
Co-authored-by: Mihai Serban <mihai.serban@gmail.com>

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 #8637

* Change indentation to 2 spaces in prompt_bzr function
* Check if in a bzr repository and optimize bzr calls in prompt_bzr

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

Fixes #8081

- Similarly to the mvn plugin
- Without this fix, the shell crashes in some cases

Co-authored-by: Marc Cornellà <marc.cornella@live.com>

Closes #4726
Closes #4774
Closes #8275

On a system with multiple batteries (like thinkpads) report percentage
and time remaining only for the active battery (the one being
discharged).

Ideally we should report all batteries, but acpi only shows time remaining
for the active battery. Also callers of these functions expect a single
return value. This is still better than reporting 596% remaining (like it
did on my laptop).

For the reference, the output of acpi command with multiple batteries looks
like this:

    Battery 0: Unknown, 5%
    Battery 1: Discharging, 86%, 03:14:04 remaining

- Fix code style
- Fix local definitions
- Don't declare unnecessary variables
- Use `command` before grep

Co-authored-by: Michael Wolman <michael.s.wolman@gmail.com>

Fixes #8614

- marks printed an error when $MARKPATH didn't exist or didn't have any marks
  in it.
- The CTRL+G key binding overwrote an argument when it couldn't match it to
  an existing mark.