Move message: make search string more flexible (i.e. not start from the beginning)

The Problem

tl;dr: current folder name search appears to be /^STRING/, but should be /STRING/i as regex

When moving a message to a folder (e.g. using the ‘v’ shortcut) the user starts typing the folder name, but has to use the exact folder name.
With lots of similar folders this is bothersome and stands in the way of productivity.
Imagine this folder structure to organize travel plans:
2022-01 DXB
2022-01 BKK
2022-02 BKK
2022-02 NYC
2022-03 KUL

If I want to move a message to the ‘2022-03 KUL’ folder I have to type at least ‘2022-03’ to get a unique hit. Typing ‘KUL’ would be unique and much more intuitive.

Additionally folder searches are limited to the mail account the message is currently in, since moving of messages across accounts is not supported (see Move emails and folders between accounts)

Proposed Solution

Allow folder name search to search middle of folder name and not start in beginning and be case-insensitive.

Alternative Solutions