It's called FakeWallet and it's used for testing the mint you fucking genius.
Discussion
Mint Bitcoin out of thin air: https://developer.bitcoin.org/examples/testing.html
Send me some testnet coins to this address: bc1p7w5xk76j3cufczuruayl0h4kv8e02q4xan3e5qxxl8yvafp2tnrqppxjge
Even I am using it for testing something.