test: add test cases for paramEncoding 'explicit'

PR-URL: https://github.com/nodejs/node/pull/27900


Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>