librlist: ensure `properties` is an array when parsing `resource.config` entries

[grondo]

There's an oversight in librlist parsing of resource.config entries, and a non-array properties value is silently ignored.

Validate that any properties entry is a JSON array and generate an error if not.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 83.28%. Comparing base (c013ee0) to head (98f1fe5).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #6029 +/- ## ========================================== - Coverage 83.29% 83.28% -0.02% ========================================== Files 519 519 Lines 83652 83655 +3 ========================================== - Hits 69680 69668 -12 - Misses 13972 13987 +15 ``` | [Files](https://app.codecov.io/gh/flux-framework/flux-core/pull/6029?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework) | Coverage Δ | | |---|---|---| | [src/common/librlist/rlist.c](https://app.codecov.io/gh/flux-framework/flux-core/pull/6029?src=pr&el=tree&filepath=src%2Fcommon%2Flibrlist%2Frlist.c&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework#diff-c3JjL2NvbW1vbi9saWJybGlzdC9ybGlzdC5j) | `85.80% <100.00%> (+0.09%)` | :arrow_up: | ... and [15 files with indirect coverage changes](https://app.codecov.io/gh/flux-framework/flux-core/pull/6029/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flux-framework)

[grondo]

Thanks! Fixed that commit message typo and will set MWP