rpc: deprecate getaddressinfo label field

Summary:
Note: the help message was already up to date (see D8214)

This is a backport of Core PR17585 [3/5]
https://github.com/bitcoin/bitcoin/pull/17585/commits/d48875fa20d0b71b978cb3d1f85dd9ec14e664cc
Depends on D8701

Test Plan:

src/bitcoind &
addr=`src/bitcoin-cli getnewaddress`
src/bitcoin-cli getaddressinfo $addr
src/bitcoin-cli stop

src/bitcoind -deprecatedrpc=label &
src/bitcoin-cli getaddressinfo $addr

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8702