Segregate the node seed from the channel seed

[dariuskramer]

Segregate the node seed from the channel seed

We want to have 2 separated seeds:

• one for the node (to sign protocol messages, etc.)
• one for the channels (to sign commit txs, etc.)

This PR creates 2 new files, nodeSeed.dat & channelSeed.dat, both stored in $datadir.

Migration from existing setup

This flow is executed twice, for nodeSeed.dat and channelSeed.dat:

+----------------------------+   Yes   +--------------------+
| Does `newSeed.dat` exists? +-------->+ Use that seed file |
+------------+---------------+         +---+----------------+
             |                             ^
             | No                          |
             v                             |
+------------+---------------+   Yes   +---+----------------------+
| Does `seed.dat` exists?    +-------->+ Copy it to `newSeed.dat` |
+------------+---------------+         +---+----------------------+
             |                             ^
             | No                          |
             v                             |
+------------+-------------+               |
| Generate a random seed   |               |
| into a file              +---------------+
+--------------------------+

The old seed.dat is not removed after the migration.

[codecov-io]

Codecov Report

Merging #1584 into master will increase coverage by 0.03%.
The diff coverage is 92.47%.

@@            Coverage Diff             @@
##           master    #1584      +/-   ##
==========================================
+ Coverage   87.21%   87.25%   +0.03%     
==========================================
  Files         140      141       +1     
  Lines       10929    10951      +22     
  Branches      460      449      -11     
==========================================
+ Hits         9532     9555      +23     
+ Misses       1397     1396       -1     

Impacted Files	Coverage Δ
...air/crypto/keymanager/LocalChannelKeyManager.scala	85.71% <68.75%> (ø)
...ir-core/src/main/scala/fr/acinq/eclair/Setup.scala	70.96% <80.00%> (+0.15%)	⬆️
...re/src/main/scala/fr/acinq/eclair/NodeParams.scala	91.12% <96.00%> (+0.86%)	⬆️
...r-core/src/main/scala/fr/acinq/eclair/Eclair.scala	55.14% <100.00%> (ø)
...c/main/scala/fr/acinq/eclair/channel/Channel.scala	85.89% <100.00%> (-0.08%)	⬇️
...in/scala/fr/acinq/eclair/channel/Commitments.scala	93.91% <100.00%> (ø)
...c/main/scala/fr/acinq/eclair/channel/Helpers.scala	96.27% <100.00%> (+0.06%)	⬆️
...q/eclair/crypto/keymanager/ChannelKeyManager.scala	87.50% <100.00%> (ø)
...eclair/crypto/keymanager/LocalNodeKeyManager.scala	100.00% <100.00%> (ø)
...-core/src/main/scala/fr/acinq/eclair/io/Peer.scala	88.58% <100.00%> (ø)
... and 8 more

[pm47]

I would move all the *KeyManager files to a sub-package of crypto.

Otherwise seems ok to me.

[t-bast]

LGTM, tiny nit

[t-bast]

LGTM