[CLEANUP] Avoid Hungarian notation for text/characters

[oliverklee]

Part of #756

[coveralls]

coverage: 50.801%. remained the same
when pulling 990e79b on cleanup/hungarian-text
into 8c770fb on main.

[JakeQZ]

I think where it is $aText it is actually an array of possibly-multibyte characters (derived by splitting with an empty 'separator'). @sabberworm, would you be able to confirm this?

Much as I'd like a quaint reference to great literary works, I think this should be renamed to $characters, which also has a similar quirky literary metaphor.

[JakeQZ]

Looking at the substr method also confirms that the formerly-named $aText property is an array of (multibyte) characters.