Add enable config parameter for legacy PNP signer endpoints

[eelanagaraj]

Description

• Tiny PR to make it possible to disable the legacy PNP signer endpoints (separately from the new PNP signer endpoints) by updating the config file (as opposed to requiring updating versions)
• For now, not doing this on the combiner side since it involves duplicating a larger section of the config file, and since we are in control of redeploying/changing the combiner, we can always allocate time as needed to do this later

driveby (unrelated to the rest of this PR but super small)

• Removed a line that looks unintentional in the common/src/test/utils file that breaks the yarn start command in the signer
• Fixes an import/removes the wallet-rpc dependency which looks like a mistake?

[alecps]

Nice!!