Update Settings Sync endpoints to account for settings_context_hash

What does this MR do and why?

• Adds validation to VsCodeSetting model to ensure that we don't set a settings_context_hash for non-extensions setting type
• Updates by_setting_types scope to only allow an array of setting types and to additionally query for settings_context_hash when setting_type = extensions.
• Update CreateOrUpdateService to save settings_context_hash for extensions settings.
• Update VsCodeSettingReference to return settings_context_hash in url if it is passed in the param.

References

• Modify update extension setting endpoint to acc... (#501283 - closed)
• Modify get extension endpoints to account for `... (#501285 - closed)

MR acceptance checklist

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Local validation/ screen recordings

Refer to the FE MR: feat: support extensions marketplace settings c... (gitlab-web-ide!392 - merged)