fix(layer order): adds placeholder for geocore layers to preserve ord…

[DamonU2]

…er added

Closes #2491

Description

Adds a place holder when calling addGeoviewLayerByGeoCoreUUID, so that the order added is preserved when adding multiple geocore layers quickly.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

https://damonu2.github.io/geoview/add-layers.html

Run the following in the console at once: cgpv.api.maps.mapWM.layer.addGeoviewLayerByGeoCoreUUID('b6b6d5a6-bded-4b6e-9e8a-17f6e1b538dc');cgpv.api.maps.mapWM.layer.addGeoviewLayerByGeoCoreUUID('6c343726-1e92-451a-876a-76e17d398a1c');cgpv.api.maps.mapWM.layer.addGeoviewLayerByGeoCoreUUID('1dcd28aa-99da-4f62-b157-15631379b170');cgpv.api.maps.mapWM.layer.addGeoviewLayerByGeoCoreUUID('3e9cc0c9-7e59-478b-befb-a584674baa75');

Order should be: heat wave, field notes, protected, water quality (reverse of added order)

Checklist:

• I have build (rush build) and deploy (rush host) my PR
• I have connected the issues(s) to this PR
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have created new issue(s) related to the outcome of this PR is needed
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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This change is 

[Alex-NRCan]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @jolevesq)

[jolevesq]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @DamonU2)