refactor: deprecate gateway mode

[swarmHaseeb]

refactor: deprecate gateway mode

Checklist

• [x] I have read the coding guide
• [x] My change requires a documentation update and I have done it
• [x] I have filled out the description and linked the related issues

Description

Deprecate gateway mode and removing all related code and update documentation

Motivation and context (Optional)

Api refactoring

Related Issue (Optional)

closes #2972

Screenshots (if appropriate):

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This change is