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
To avoid code changing underneath the static migrations, we copy the
lnwire dependency in its current form into the migration directory.
Ideally the migrations doesn't depend on any code that might change,
this takes us a step closer.
This commit copies over the relevant zpay32 decoding logic to ensure
that our prior migrations aren't affected by upcoming changes to the
zpay32 package, most notably changes to the default final_cltv_expiry
and expiry values.
