Allow disabling broadcast for name_new/firstupdate/update

[JeremyRand]

Is your feature request related to a problem? Please describe.

The send RPC method supports disabling broadcast of the resulting transaction via the add_to_wallet and psbt options, which make it just return a serialized raw transaction or PSBT instead. (Electrum-NMC's RPC method support this for both currency and name transactions.) Unfortunately, these options are not supported by the name RPC methods.

Describe the solution you'd like

Add the add_to_wallet and psbt fields to the options parameter of the name RPC methods, so that name transactions have feature parity with currency transactions.

Describe alternatives you've considered

N/A.

Additional context

N/A.