OSDOCS-1927: Add file-based catalog docs

[adellape]

https://issues.redhat.com/browse/OSDOCS-1927

Preview:

• New concept sections: "Operator Framework packaging format → File-based catalogs"
• New procedure section: "Managing custom catalogs → Creating a file-based catalog image"
• For the existing procedures in "Managing custom catalogs" that were about the SQLite format but just referred plainly "index images" (we never actually called out the SQLite database format by name before really), I've renamed those sections with more explicit titles like "Creating a SQLite-based index image" and added a deprecation notice.
• Because the RH-provided catalogs are still using SQLite, I left the "Using Operator Lifecycle Manager on restricted networks" topic using the older SQLite procedures for now, though I could see a need for both if they were also using file-based for their custom catlogs... Let me know if I should rework that topic too to include either option.
• New "opm CLI reference" topic
  • Introduces an "opm" subdirectory for the "CLI tools" guide to accommodate the new reference topic, instead of just previously having one single topic for opm.

Note: Related 4.9 release notes are being added via #36467.

[netlify]

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😎 Browse the preview: https://deploy-preview-36352--osdocs.netlify.app/openshift-enterprise/latest/cli_reference/opm/cli-opm-install

[bmcelvee]

Couple of suggestions, but it's looking good!

[adellape]

/cherrypick enterprise-4.9

[openshift-cherrypick-robot]

@adellape: new pull request created: #36966

Details

In response to this:

/cherrypick enterprise-4.9

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