Themes: use _save-and-reload-history()

[gaelicWizard]

Description

Replaces

history -a
history -c
history -r

with a single call to _save-and-reload-history() in all themes. Alsö, remove executable bit.

Motivation and Context

This is inspired by #1595 and does not depend on #1940, so I made a separate PR.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.

[NoahGorny]

Nice work!
This should not change any behaviour, right?

[gaelicWizard]

Nice work!
This should not change any behaviour, right?

In this PR, I specifically only replaced calls to all three lines with the function that calls all three lines. There should be absolutely no behavior changes.