Summary

Implements Vitest environment helpers to avoid direct manipulations on process.env

Changes

1. Main Changes:

• Replacing direct process.env manipulations with Vitest's environment helper functions:
  • Using vi.stubEnv() to set environment variables
  • Using vi.unstubAllEnvs() to clear environment variables
  • Removing manual environment variable backups and restorations

2. Files Modified:

• packages/logger/tests/unit/formatters.test.ts
• packages/logger/tests/unit/initializeLogger.test.ts
• packages/logger/tests/unit/injectLambdaContext.test.ts
• packages/logger/tests/unit/logBuffer.test.ts
• packages/logger/tests/unit/logEvent.test.ts
• packages/logger/tests/unit/logLevels.test.ts

3. Pattern of Changes:

• Removing const ENVIRONMENT_VARIABLES = process.env storage
• Adding afterEach hooks with vi.unstubAllEnvs()
• Replacing process.env = {...} assignments with vi.stubEnv()
• Moving logger instance creation into beforeEach blocks

Please add the issue number below, if no issue is present the PR might get blocked and not be reviewed

Issue number: closes #4269

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