Enable host lookups for -proxy and -onion parameters

Summary:

• Extends -dns parameter (via fNameLookup) to control these two new parameters in addition to -addnode, -connect, and -seednode

• Moves fNameLookup assignment earlier as needed

• Changes -proxy and -onion to use Lookup() instead of LookupNumeric()

This is backport of Core PR9774

Test Plan:

make check

Reviewers: #bitcoin_abc, schancel

Reviewed By: #bitcoin_abc, schancel

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1753