support Wallet names with hyphens when passing password through ENV vars

[mjurbanski-reef]

Description of the Change

Support Wallet names with hyphens when passing password through ENV vars

Alternate Designs

Another solutions would be to:

• Explicitly discourage (disallow?) creating wallet names with hyphens - naming is hard problem, so it would likely rattle some people

Possible Drawbacks

A possible drawback is if someone had multiple wallets which only difference was that one had - instead of _, but that seems VERY unlikely.

Verification Process

Added unittest case + manual testing.

Release Notes

• BT_COLD_PW_* env vars now can be used to provide password for wallet names with hyphens (use _ in place of -)