Refactors prettier support:

* moves away prettier-related code into a separate module, makes
prettier installation & start phases more type-restricted
* ensures prettier installation and start attempts are capped with a
fixed attempts amount: after it's exceeded, no further attempts to
install and/or start prettier area made
* improves default prettier management, by correctly preserving its
plugin set between (re) installations and always installing the prettier
server part
* slightly improves prettier logging 

Release Notes:

- N/A