test:migrate JUnit 4 + PowerMock to JUnit 5 + Mockito in logger-admin,opentelemetry modules

[drow931]

migrate tests from JUnit 4 + PowerMock to JUnit 5 + Mockito in logger-admin,opentelemetry

Summary

This PR continues the test framework migration effort, updating test classes
in trpc-logger and trpc-opentelemetry modules.

Changes

Test Migration

• trpc-logger-admin: Migrate 6 test classes to JUnit 5 + Mockito

  • Log4j2LoggerProcessUnitTest
  • LogbackLoggerProcessUnitTest
  • LoggerLevelInfoTest
  • LoggerManagerTest
  • LoggerProcessUnitFactoryTest
  • UnSupportLoggerProcessUnitTest

• trpc-opentelemetry: Migrate 2 test classes to JUnit 5 + Mockito

  • OpenTelemetryFactoryTest
  • TrpcFilterTest

Code Improvements

• Replace @Before/@After with @BeforeEach/@AfterEach
• Replace Assert.* with Assertions.*
• Replace PowerMockito.mockStatic with Mockito.mockStatic (try-with-resources)
• Replace ExpectedException.expect() with assertThrows()
• Add reflection-based static field reset for singleton test isolation