Improve Code Coverage % for Azure

• issue Reference: osdu/platform/ci-cd-pipelines#40
• refactored the existing testcases to run on Junit5
• added missing testcases scenarios/branches for
  • PartitionSecretClientResolver.java
  • KeyVaultUrlProvider.java
  • SecretManagerImpl.java
• Added 'jacoco-maven-plugin' configuration exclusion list [SpringBootApplication class & Configuration classes/packages]
• formatted the test cases w.r.t Arrange Act Assert [AAA] pattern & naming conventions(should_when)
• Azure Code Coverage Report Current MR vs master