Add pseudo_pending for ms/mr/md

[AceofSpades5757]

implements #3223

Adds pseudo pending text for ms/mr/md commands (match surround, replace, and delete).

Currently hard-coded as there appears to be an issue with appending to the current editor.pseudo_pending value.

• Can leave it open to not be cleared on the next key press. Leaves lingering pseudo text.
• Can append it, only to have it immediately cleared (appending in the target locations would be cleared immediately before appending).

[AceofSpades5757]

It looks like pseudo_pending is affected by initial key maps such as <space>, or anything else opening an auto_info windows. I was unable to find where this is located, or how it is handled. If possible, it would have been nice to implement this same functionality for similar situations that wait on a key press, but that may be out of scope for this pr and issue.

[the-mikedavis]

Surround-replace has two cx.on_next_keys, one for the starting character and one for the replacement. Nested in the first cx.on_next_key, we should add the character from the event to the pseudo-pending and then clear it within the second

[AceofSpades5757]

Thanks, I'll take a look at that.