Yuhsuan/stores null check

[YuHsuan-Hwang]

Description

This PR is for #2343 migrating part of the files in /stores to strictNullChecks enabled. The rest of the files in /stores will be migrated in a separate PR.

Some additional changes:

• CatalogPlotWidgetStore fitting, minMaxX, and statistic: set the entire variable to null instead of setting all members to undefined.
• Adjusted PvGeneratorWidgetStore setSpectralCoordinate and setSpectralSystem.
• Fixed the returned values in SpectralLineQueryWidgetStore.filters. Return an array of filter strings instead of an array of headers.
• Fixed incorrect telemetry data in SpectralProfileWidgetStore.requestMoment. Send the info of the selected region (either active or a specific id) instead of the active region.

Checklist

For linked issues (if there are):

• assignee and label added
• GitHub Project estimate added

For the pull request:

• reviewers and assignee added
• GitHub Project estimate added
• changelog updated / no changelog update needed
• unit test added (for functions with no dependenies)
• API documentation added (for public variables and methods in stores)

For dependencies:

• e2e test passing / corresponding fix added / new e2e test created
• protobuf version bumped / no protobuf version bumped needed
• protobuf updated to the latest dev commit / no protobuf update needed
• corresponding ICD test fix added (BackendService changed) / no ICD test fix needed (BackendService unchanged)
• user manual prepared (for large new features)

[kswang1029]

As picked up by the e2e tests, when we select a casa image or a miriad image in the file list, the file info cannot be displayed. fits and hdf5 are fine.

[YuHsuan-Hwang]

Fixed failed e2e tests.

[kswang1029]

When we have a spectral profile plot, if we switch the x-axis to "channel", we cannot click a channel to switch to the channel in the image viewer. We cannot zoom/pan the spectral profile plot neither.

[YuHsuan-Hwang]

When we have a spectral profile plot, if we switch the x-axis to "channel", we cannot click a channel to switch to the channel in the image viewer. We cannot zoom/pan the spectral profile plot neither.

This is fixed.