Using the tor module instead of whole lnd in healthcheck allows us to get rid of a lot of indirect dependencies.
This commit was previously split into the following parts to ease review: - 2d746f68: replace imports - 4008f0fd: use ecdsa.Signature - 849e33d1: remove btcec.S256() - b8f6ebbd: use v2 library correctly - fa80bca9: bump go modules
Upgraded the go to 1.16 for the rest of the packages.