Handle more variety in user input for `server` argument in `board_connect()`

[juliasilge]

For board_connect() with auth managed by the rsconnect package, we use some pretty exact matching for how rsconnect::accounts() keeps track of servers:

pins-r/R/board_connect_server.R

Line 81 in 0d6d7f0

accounts <- rsconnect::accounts()

We do document how you are supposed to use this argument:

pins-r/R/board_connect.R

Lines 58 to 61 in 0d6d7f0

	#' @param server For `auth = "manual"` or `auth = 'envvar'`, the full url to the server,
	#' like `http://server.posit.co/rsc` or `https://connect.posit.co/`.
	#' For `auth = 'rsconnect'` a host name used to disambiguate Connect accounts,
	#' like `server.posit.co` or `connect.posit.co`.

However, we could make this more lenient by parsing the value the user has and taking the schema off, if it is there.