turn dictation helpers into actions to make them configurable

[chdoc]

The motivation for this change is my current work on German mode, which implements these new actions as follows:

# characters to replace if ASCII punctuation is desired
_ascii_replace = {'–': '-', '„': '"', '“': '"', "‚": "'", "‘": "'", "’": "'"}
_ascii_trans = str.maketrans(_ascii_replace)

@ctx.action_class("user")
class Actions:
    def omit_space_before(text: str) -> bool:
        return bool(not text or text[0] in _no_space_before)

    def omit_space_after(text: str) -> bool:
        return bool(not text or text[-1] in _no_space_after)
    
    def dictation_replace(text: str) -> str:
        if settings.get("user.german_unicode"):
            return text
        return text.translate(_ascii_trans)

Note that the rules regarding spacing around quotes are very different between English and German. In particular, the English opening quote is the German closing quote.