When external signer support is not compiled, do not load external signer wallets.
Alternative to #22168.
When external signer support is not compiled, do not load external
signer wallets.
Tested ACK e60cd26ad46559770ad84d2959c9a1742ae8b7a6.
Code review ACK e60cd26ad46559770ad84d2959c9a1742ae8b7a6
Milestone
22.0