Fix feature_signet functional test case

[gitcoindev]

Description

Goal of the pull request is to fix failing feature_signet functional test case.

The main challenge was to enable failing BGL signet initialization and mine blocks on a custom BGL Signet network. I was able to achieve it following instructions available at https://en.bitcoin.it/wiki/Signet

This updated test case uses custom signet network generated for ADDR rbgl1q2lk0e5yjen2vq9pknxcr6xc32wp4hhpa8fgk2x and PRIV key cQ7AMSUGQcAPy3HwVRaZqAqnC4eVaAF8naEWekPHoodmV7uFw4kA and PUB key 03d47f70342433a1e56def6965f63ac147f5292a2054dfba4b98535a87d32f13db

Mined 10 blocks with payout to tb1qnl2gquva8mzuc05y3pvad43vvju43wf0utk4eh with BGL signet network configuration:

signet=1
[signet]
signetchallenge=512103d47f70342433a1e56def6965f63ac147f5292a2054dfba4b98535a87d32f13db51ae

and BGL signet mined block hashes:
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Notes

$ test/functional/feature_signet.py 
2023-01-04T14:31:08.877000Z TestFramework (INFO): Initializing test directory /tmp/BGL_func_test_ufnx3bd9
2023-01-04T14:31:09.750000Z TestFramework (INFO): basic tests using OP_TRUE challenge
2023-01-04T14:31:09.750000Z TestFramework (INFO): getmininginfo
2023-01-04T14:31:09.752000Z TestFramework (INFO): pregenerated signet blocks check
2023-01-04T14:31:09.788000Z TestFramework (INFO): pregenerated signet blocks check (incompatible solution)
2023-01-04T14:31:09.789000Z TestFramework (INFO): test that signet logs the network magic on node start
2023-01-04T14:31:10.252000Z TestFramework (INFO): Stopping nodes
2023-01-04T14:31:10.465000Z TestFramework (INFO): Cleaning up /tmp/BGL_func_test_ufnx3bd9 on exit
2023-01-04T14:31:10.465000Z TestFramework (INFO): Tests successful