Transition network key to hex format

[AgeManning]

Issue Addressed

#7181

Proposed Changes

Instead of storing the network key as binary data we store it as hex, allowing users to modify it via the file.

We can read old-binary forms, however we will migrate binary to hex as it will be the new standard.

[michaelsproul]

Noting that this isn't backwards compat because old versions of LH won't work with the hex-formatted keys.

[jimmygchen]

Looks good!

[mergify]

This pull request has been removed from the queue for the following reason: checks failed.

The merge conditions cannot be satisfied due to failing checks:

• ☑️ test-suite-success

You can check the last failing draft PR here: #7881.

You may have to fix your CI before adding the pull request to the queue again.
If you update this pull request, to fix the CI, it will automatically be requeued once the queue conditions match again.
If you think this was a flaky issue instead, you can requeue the pull request, without updating it, by posting a @mergifyio requeue comment.

[jimmygchen]

@mergify requeue

[mergify]

requeue

✅ The queue state of this pull request has been cleaned. It can be re-embarked automatically