psql not responding to SIGINT upon db reconnection

Neon provides a quick start mechanism for psql using the following 
workflow:

	$ psql -h pg.neon.tech
	NOTICE:  Welcome to Neon!
	Authenticate by visiting:
	    https://console.neon.tech/psql_session/xxx

Upon navigating to the link, the user selects their database to work 
with. The psql process is then connected to a Postgres database at Neon.

psql provides a way to reconnect to the database from within itself: \c. 
If, after connecting to a database such as the process previously 
mentioned, the user starts a reconnection to the database from within 
psql, the process will refuse to interrupt the reconnection attempt 
after sending SIGINT to it. 

	tristan=> \c
	NOTICE:  Welcome to Neon!
	Authenticate by visiting:
	    https://console.neon.tech/psql_session/yyy
	
	^C
	^C^C
	^C^C

I am not really sure if this was a problem on Windows machines, but the 
attached patch should support it if it does. If this was never a problem 
on Windows, it might be best to check for any regressions.

This was originally discussed in the a GitHub issue[0] at Neon.

[0]: https://github.com/neondatabase/neon/issues/1449

-- 
Tristan Partin
Neon (https://neon.tech)