Consolidate devfile docs by pulling in generic content from odo devfile docs

[Preeticp]

Is your feature request related to a problem? Please describe.

Currently we maintain two copies of devfile reference docs in odo and in devfiles repos.

Describe the solution you'd like

Based on discussions between DV, Elson and Tim in the Sprint review call for track 2, it was recommended that all generic devfile content in this doc: https://odo.dev/file-reference/ should move to the devfile docs and the odo docs must reference the devfile docs and link to the devfile spec. If there's anything odo-specific we can leave it on odo.dev, but we need to redirect anything else to the devfile docs.

Additional context
Parallel odo issue:
redhat-developer/odo#4372

[rkratky]

Thanks for filing this, @Preeticp. The sooner we get this done, the the easier it will be to promote one and only canonical place for the devfile reference.

@jc-berger, please, work with @boczkowska on the odo side to:

1. Identify odo-specific stuff from the odo-published reference
2. Publish all generic stuff on the devfile website
3. Publish a whittled down version (with odo-specific things only) on the odo site with links to the devfile site

[rkratky]

JIRA: https://issues.redhat.com/browse/RHDEVDOCS-2530

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