[Extensions] Create a XContentParser for ExtensionScopedSettings

[owaiskazi19]

Is your feature request related to a problem? Please describe.
As a part of opensearch-project/opensearch-sdk-java#782 a new design for initialization has been done here #8029. To process the request body with additionalSettings a XContentParser is needed here.

Describe the solution you'd like
Create a XContentParser for ExtensionScopedSettings to read additonalSettings

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.