Add configuration related to cache layer for OAuth2 token validation in REST API

[AqeelMuhammad]

Current Limitation

The current API documentation does not contain the details and the configurations related to the improvement in the cache layer for OAuth2 token validation in the REST API.

Suggested Improvement

Add the configurations related to the change done in the PR [1]

[1] wso2/carbon-apimgt#7342

Refer to the APIM internal-7432 issue for more details

Version

All APIM Versions