Fix gp_log_collector to query database for actual log directory path

[Copilot]

The gp_log_collector command was hardcoding the log directory path as $HOME/gpdb/gp-master/gpseg-1/pg_log, which often doesn't exist in actual Greenplum installations. This caused the command to fail with:

Error collecting logs: failed to walk log directory: lstat /home/gpadmin/gpdb/gp-master/gpseg-1/pg_log: no such file or directory

The fix implements the suggested solution by querying the database first to get the actual log directory:

select distinct datadir || '/log' from gp_segment_configuration where content='-1';

Changes Made

• Added getLogDirectoryFromDB(): Queries the database for the actual coordinator log directory path
• Enhanced error handling: Uses panic recovery to gracefully handle database connection failures
• Smart fallback: When database is unavailable, falls back to the existing hardcoded path behavior
• Preserved compatibility: All existing command-line flags and functionality remain unchanged

Behavior

• With database available: Uses the real log directory from gp_segment_configuration
• Without database: Gracefully falls back to the previous hardcoded path logic
• Debug logging: Provides clear information about which method is being used (--verbose flag)

The fix ensures gp_log_collector works correctly in real Greenplum environments while maintaining backwards compatibility for edge cases where the database query might fail.

Fixes #13.

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