storage: create a protobuf to hold stores

[andrewbaptist]

Summary of changes:

• Create a struct configpb.Storage to represent all the "store related" pieces (mostly store config and WAL failover)
• Move the encryption code into the configpb directory and delay "serialization" of the encryption options.
• Remove all direct reads of the Stores from server.Config, instead use the new StorageConfig
• Various cleanups to pass the configpb.Storage or configpb.Store in construction
• Persisting the StorageConfig on each of the stores
• Addition of a bootstrapConfig option which allows reading the config from either the OS disk or one of the existing disks.

WIP: This commit will be split up eventually.
Epic: none

Release note: None

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

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[cockroach-teamcity]

This change is 

[blathers-crl]

Your pull request contains more than 1000 changes. It is strongly encouraged to split big PRs into smaller chunks.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}