Create and manage Tigris bucket for PG/Barman backups

[ndarilek]

Change Summary

Integrates the new Tigris WAL storage into flyctl.

• Provisions a new Tigris bucket on cluster creation and sets the barman secret appropriately.
• Adds a --disable-backups flag to fly pg create command to disable bucket/secret provisioning on cluster creation.
• Adds a currently non-functional fly pg backup enable command for provisioning buckets and secrets into clusters where WAL backup is disabled.
• Adds fly pg backup create for creating backups, optionally named.
• Adds fly pg backup list to list existing backups.

Related to:

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Documentation

• [ ] Fresh Produce
• [ ] In superfly/docs, or asked for help from docs team
• [ ] n/a

[benwaffle]

If the bucket name is already taken, we should generate a unique name instead of erroring out