WIP: Actions: Make edit-clear more consistent

[newhoa]

@danirabbit , you mentioned in the issue

GitHub search and see where edit-clear is used and switch all of those instances to edit-clear-all with fallbacks enabled...

I wasn't totally sure what enabling the fallbacks meant or where exactly to look. I checked for symlinks and the like and didn't find any that needed changing, but wasn't sure what more to do (edit: see followup reply). The rest I think should be on the right track. Moved edit-clear Broom icons to edit-clear-all, make edit-clear all use the red Backspace symbol. I did add the error class to the symbolic edit-clear icons to make them red if that is okay.

One thing I'm not sure on is the sizes. I did a new edit-clear based on the mail-mark-important icon (as mentioned in the issue) at 16px. Should this be done at other sizes? I'm not sure that these icons are used beyond the text-entry boxes (16px) or possibly toolbar icons (24px), so I'm not sure that 32x, 48px, etc are needed (and if not should the larger edit-clear-all icons be removed as well?).

Current:

Proposed:

Also played with making the new regular edit-clear a few pixels longer vs a little more square (edit-clear0), wasn't sure which to go with but I like the longer one a little more, it's a bit more legible:

Git Log:

• edit-clear: red backspace symbol
• edit-clear-symbolic: red backspace symbol, error class added
• edit-clear-all and edit-clear-all-symbolic: broom symbol

Fixes #1126

[newhoa]

If by Github search you meant search other projects, it looks like there might be 3 places in other projects:

• switchboard-plug-printers: dialog
• installer: try install view
• icon-browser: category view

[newhoa]

I'll also add, while edit-clear is in the freedesktop.org icon naming spec, edit-clear-all is not.

In places where they are used, there doesn't seem to be any actionable difference between the two -- they both clear all.