[GOBBLIN-2243]Add Fallback dir for Jar caching

[pratapaditya04]

Dear Gobblin maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following Gobblin JIRA issues and references them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
  • https://issues.apache.org/jira/browse/GOBBLIN-2243

Description

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  Add Jar Cache Directory Validation with Fallback
  Summary
  Implements validation for jar cache directories with automatic fallback handling in GobblinYarnAppLauncher.
  Changes
  Added addJarCachingConfig() method: Validates JAR_CACHE_DIR exists on filesystem, falls back to FALLBACK_JAR_CACHE_DIR if not found, or disables jar caching if neither exists

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
  Added unit tests

Commits

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  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

[khandelwal-prateek]

computing JAR_CACHE_DIR from filesystem state at config load time makes it hard to debug. We can introduce a JarCachePathResolver instead that computes the resolved cache dir, when needed.

If that's too big a change, for now, let's check that JAR_CACHE_DIR is not already explicitly configured(if it is, use it as is) to avoid overriding an existing config.

[pratapaditya04]

makes sense, removed logic from constructor , made JarCachePathResolver