Add additional device tests for GRS
Add P2TR GetAddress for GRS mainnet and testnet
Add SignTX spending taproot UTXO (The resulting transaction from the SignTx device test was successfully mined on Testnet.)
Enable 'confidential_assets' for Elements (following #66 and #317) to allow
deriving confidential addresses and signing confidential transactions.
The following Python helper script was used to update the JSON files:
```
import json
import sys
for f in sys.argv[1:]:
d = json.load(open(f))
d["confidential_assets"] = None
with open(f, "w") as o:
json.dump(d, o, indent=2)
o.write("\n")
```
Set it to `{'address_prefix': 4, 'blech32_prefix': 'el'}` for Elements.
`coins.json` and `coininfo.py` were re-generated using:
```
$ pipenv run make gen gen_check
```
