Display the network limited flag in peer details

Summary:
Display "LIMITED" for network limited nodes.
Note that the avalanche flag is not displayed, because it is in the
experimental range.

Test Plan:

./src/qt/bitcoin-qt -prune=550 &
mkdir /tmp/datadir
./src/qt/bitcoin-qt -datadir=/tmp/datadir -connect=127.0.0.1

In the second instance:
Go to "Help=>Debug window"
Select the tab "Peers"
Click the 127.0.0.1 peer in the upper table
Check in the details that the LIMITED flag is displayed

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2442