Integrate hclog

[egourlao]

With this pull request, memberlist uses hclog.Logger as logging interface.

Here are a few other changes that this commit integrates:

• The Config and NetTransportConfig are changed, and now take directly the hclog.Logger object. If no object is passed, newMemberlist uses hclog.Default().
• fromAddress and fromConn are now methods of a struct that embeds hclog.Logger.
  • Given that the way those methods are called has changed, tests have also changed.
• To log errors, I drew inspiration from other projects using hclog and added them with the "err" field name.

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[tyndyll]

Is there any way to move this forward?

[dnephin]

You can use hclog with memberlist by calling Logger.StandardLogger (https://pkg.go.dev/github.com/hashicorp/go-hclog#Logger), and passing that in as the Logger:

logger := hclog.New(nil)
logger.StandardLogger(&hclog.StandardLoggerOptions{InferLevels: true})

This PR seems to have many merge conflicts, so it would probably be easier to start from scratch. If someone were to do that, it might be preferable to accept an interface that can be satisfied by hclog instead.