Allowed launchd plists missing optional fields

[Spferical]

One line description of pull request

This fixes parsing of launchd plists that are missing optional fields.

Description:

I noticed many launchd plists failing to emit any events. According to apple docs, Label and ProgramArguments are required. In practice, it looks like ProgramArguments is also optional, with many LaunchDaemon plists on my macos 13.6 system having only Program set.

Notes:

All contributions to Plaso undergo code review. This makes sure that the code has appropriate test coverage and conforms to the Plaso style guide.

One of the maintainers will examine your code, and may request changes. Check off the items below in order, and then a maintainer will review your code.

Checklist:

• [x] Automated checks (GitHub Actions, AppVeyor) pass
• [x] No new new dependencies are required or l2tdevtools has been updated
• [x] Reviewer assigned

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 76.47059% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 85.16%. Comparing base (25b533b) to head (40432ed). Report is 1 commits behind head on main.

Files	Patch %	Lines
plaso/parsers/plist.py	60.00%	2 Missing :warning:
plaso/parsers/plist_plugins/launchd.py	77.77%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4803 +/- ## ========================================== - Coverage 85.16% 85.16% -0.01% ========================================== Files 427 427 Lines 38614 38623 +9 ========================================== + Hits 32886 32893 +7 - Misses 5728 5730 +2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[joachimmetz]

Spferical requested a review from joachimmetz 7 hours ago

I'll take another look when time permits

[joachimmetz]

https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html section "Required and recommended property list keys" indicates ProgramArguments is also a required key

And I see you mention this in your original post

In practice, it looks like ProgramArguments is also optional, with many LaunchDaemon plists on my macos 13.6 system having only Program set.

[joachimmetz]

@Spferical PTAL if the additional changes match your requirements

[Spferical]

@Spferical PTAL if the additional changes match your requirements

Looks great to me, thank you!