feat: improve config

Description

Make config

• Reorder the blocks
• Comment each param (except the retrieval section, it's on TODO), improve existing comments
• Split the example config to separate configs, corresponding to concrete use cases: logical dump/restore, RDS, physical, WAL-G.

TODO for the next iteration:

• "physical generic" is empty now, needs to be done soon
• retrieval is not reviewed/improved yet -- also to be done in the next iteration.
• also see separate TODO for the code refactoring below.
• proofread all the texts

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes, specifications reflect those changes and they have been reviewed OR there are no API changes

Additional TODO (follow up items, not for this MR)

• reduce the number of config sections
• move debug inside the global section
• get rid of stages concept, use only jobs
• global.dataDir:
  • rename to mountPoint or smth like this. The idea is to avoid duplicating part of of the path (now, provision.pgDataSubdir is suffix of global.dataDir - this looks weird and not intuitive)
  • also, where should it be -- in provision, and retrieval should be also part of provision?
• provision.pgDataSubdir
  • get rid of leading slashes. When concatenating, add slash automatically. Otherwise, it looks weird -- it starts with /, so it looks like absolute path
  • so, default value becomes an empty string, not '/'
• retrieval but provision – a noun vs a verb. Not really consistent
• idea: always use double-quoted values in the example configs?
• do we need provision.pgMgmtUsername at all?
• hide provision.mode - it has only one option, we don't need to show it.
• explicitly use the worh "clone" in provision.mountDir -- to emphasize that this option deals with clones.
• provision.snapshotFilterSuffix is a "negative" filter but it's not clear from the name. Use the word "exclude"
• global.dockerImage and provision.dockerImage:
  • we need just one. Two -- too much. And by default, it should be an extended image from us.
  • and there is one more dockerImage, the 3rd, in logical retrieval jobs description -- It's too much.
• for logical-dump job, use "imediate" word in restore to indicate that restoration will happen immediately, without saving the dump file on disk.
• get rid of cloning.mode -- we have only base
• for physical-restore, fix walg storage options. It almost doesn't matter for cloud storages except for GCS
• merge retrieval to provision