Optimize file discovery by adding skipPermissionCheck flag

[thevyom1]

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-XXX

Description

This PR introduces a performance optimization for file discovery by adding a skipPermissionCheck flag.

Key changes:

• Added skipPermissionCheck flag to skip I/O operations for files that already exist in the target location
• When enabled, skips expensive file status checks and permission resolutions for existing files
• Improves performance for discovery by avoiding unnecessary I/O operations
• Disabled by default to maintain backward compatibility

This change is particularly beneficial for large-scale copy operations where file existence checks can be a significant performance bottleneck.

Tests

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

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  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"