FeatureServer fixes

[na9da]

What this PR does

• Apply clipping rectangle in tiled mode. This reduces the number of requests made in tiled mode.
• Adds clipToRectangle trait if we want to turn off the rectangle clipping
• Fix a few reactivity issues that resulted in reloading of layers when unrelated traits change.
• Proxy imageryprovider requests

Test me

1. Fewer FeatureServer requests when loading layers in this branch vs main. I found this makes some noticeable difference on slower servers.
2. Load this layer in main, once fully loaded, click collapse all in the workbench, see that the layer gets re-loaded (due to change in unrelated traits). Try the same with this branch, it shouldn't react to changes in unrelated traits.

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.

[na9da]

loadMetadatResult returns a new Result object after each call to loadMetadata which causes this method to recompute unnecessarily. Instead check if the strata exists.

[na9da]

Memoize outFields etc. This is also required to stop the imageryProvider from re-comping when for example a user strata gets added to the object.

[nf-s]

Looks good!

Only issue is that requests to https://services1.arcgis.com are now being proxied through TerriaJS-server - and it is very slow. So we need to add arcgis.com in corsDomains I think - or remove it from allowProxyFor

[na9da]

Thanks @nf-s. Good point. I have created a PR here to remove arcgis.com from proxied list - TerriaJS/TerriaMap#756