Modify get extension endpoints to account for `settings_context_hash`

MR: Update Settings Sync endpoints to account for s... (!172748 - merged)

Description

We want to update the get setting endpoints to consider the different settings_context_hash when the setting type is extensions. These endpoints include:

• /v1/manifest
• /v1/resource/:resource_name
• /v1/resource/:resource_name/:id

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NOTE: The settings_context_hash is only considered when the setting type is extensions. Otherwise we read/write to the "default"/nil one is.

Acceptance Criteria

• The returned extensions setting in the response corresponds to the settings_context_hash passed in the route parameter if it exists.
• Note: Let's consider adding integration/request spec either here or in Modify update extension setting endpoint to acc... (#501283 - closed).

Technical Requirements

• Update SettingsFinder logic such that if the setting type is extensions, we will also query by settings_context_hash which is passed in the route parameter.