Switch bwcli to using the new bw serve command

[firecat53]

Bitwarden CLI v1.22.0 added a serve option to interact with the vault using a REST API. It seems faster than calling commands via subprocess, although need to wait to actually finish it publicly until they release the fix that binds the API to localhost. Right now it's wide open to the network.

Basic interaction:

items = 'http://localhost:8087/unlock'
headers = {'accept': 'application/json'}
payload = {'password': 'mypassword'}
res = requests.get(items, headers=headers, json=payload)

Probably start bw serve either in the main server process or perhaps in a separate thread that can be restarted with a different BITWARDENCLI_APPDATA_DIR to allow multiple vaults to be accessed.