Refactor execution handler validation and version bump

[jessehouwing]

Improve clarity and consistency in the validation of execution handlers while updating the version.

This pull request refactors and improves the validation logic for task execution handlers in app/lib/jsonvalidate.ts, ensuring more robust and comprehensive validation across different execution types. It also bumps the package version in package.json to reflect these changes.

Validation logic improvements

• Refactored execution handler validation by introducing the validateAllExecutionHandlers and validateExecutionTarget helper functions, allowing validation of execution, prejobexecution, and postjobexecution blocks uniformly.
• Ensured that the validation function always returns an array of issues, even when the execution block is missing, preventing undefined return values for tasks without execution configuration.
• Improved file existence checks for execution targets, including normalization of the target path and handling of variable substitutions.

Package version update

• Updated the version in package.json from 0.22.0 to 0.22.1 to reflect these validation improvements.

Fixes: #511

[jessehouwing]

@tarunramsinghani

[tarunramsinghani]

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