fix: filter object env vars in fork mode and fix CLI option mapping

[amussara]

Fixes #6073: PM2 passes object properties as '[object Object]' environment variables to subprocesses in fork mode. Added sanitizeProcessEnv() function that filters out non-primitive values (objects, arrays) before passing env to child_process.spawn().

Fixes #5208: --stop-exit-codes CLI option was not recognized because Config.filterOptions() only checked explicit schema aliases. Enhanced filterOptions() with snakeToCamel() helper to automatically map commander.js camelCase options (e.g. stopExitCodes) to their snake_case schema keys (e.g. stop_exit_codes). This fixes all CLI options with hyphens that correspond to underscore-separated schema keys.

Also added explicit 'stopExitCodes' alias to the stop_exit_codes schema entry for additional clarity.

Q	A
Bug fix?	yes/no
New feature?	yes/no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#1234, #5678
License	MIT
Doc PR	https://github.com/pm2-hive/pm2-hive.github.io/pulls

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