Fix and validate "version" field while importing metadata in local monitoring

[shreyabiradar07]

Currently version is not used in the current local monitoring datasource codeflow and hence POST /dsmetadata API passes and imports metadata successfully even with blank and invalid input json version field values.

Associated test case failure in local_monitoring_tests: rest_apis.test_import_metadata.test_import_metadata_invalid_test[blank_version-400--prometheus-1] rest_apis.test_import_metadata.test_import_metadata_invalid_test[invalid_version-400-xyz-prometheus-1]