Set headers for URLs proxied from Cesium ion

[ggetz]

Description

This PR tidies a bit of handling for imagery assets proxied via a Cesium ion asset, including Google 2D Imagery and shortly, Azure Imagery. It ensures we are including the X-Cesium-Client-* headers that are typically sent to ion URLs.

• Previously, we treated proxied assets as "external". This meant we were omitting headers and requesting images in a slightly different different way. Now, the endpoint options are modified such that assets that are proxied are treated like typical ion imagery.
• Tidies up special handling for Google2DImageryProvider and Azure2DImageryProvider so that their logic is now isolated to one file: IonImageryProviderFactory.
• I pulled out logic from IonImageryProvider into IonImageryProviderFactory because 1) The former file was getting big and unwieldy, but now 2) we can call the logic from other places without creating a circular dependency on IonImageryProvider, allowing us to simplify Google2DImageryProvider.fromIonAssetId a bit.
• Various testing cleanup, namely per jasmine's sharing behaviors recommendations, and minor source code changes to facilitate.

Issue number and link

Fixes #13000

Testing plan

1. Confirm various imagery types—including Bing, Google 2D, ArcGIS, etc—still work as expected
   • With the debugger in the Network tab, confirm the imagery requests to assets.ion.com include the X-Cesium-Client and X-Cesium-Client-Version headers.
   • Confirm imagery requests to external (non-cesium.com urls) do not include these headers.

2. Confirm existing Google 2D Imagery API via IonImageryProvider.fromAssetId properly refreshes sessions.
   • Open local sandcastle or deployed equivalent
   • Wait ~3 seconds to invalidate the original session
   • Navigate around to load new tiles. It's ok to see some error messages in the console while the session token is being refreshed, but they should quickly stop.
   • Confirm the refreshed imagery requests to assets.ion.com include the X-Cesium-Client and X-Cesium-Client-Version headers
3. Confirm existing Google 2D Imagery API via Google2DImageryProvider.fromIonAssetId properly refreshes sessions.
   • Open local sandcastle or deployed equivalent
   • Wait ~3 seconds to invalidate the original session
   • Navigate around to load new tiles. It's ok to see some error messages in the console while the session token is being refreshed, but they should quickly stop.
   • Confirm the refreshed imagery requests to assets.ion.com include the X-Cesium-Client and X-Cesium-Client-Version headers

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change This should not affect users, so I did not update CHANGES.md
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @ggetz!

✅ We can confirm we have a CLA on file for you.

[ggetz]

@lukemckinstry Could you please review? This may make sense to merge before #13001.

[lukemckinstry]

The Google Contour asset (id: 3830186) throws this error in http://localhost:8080/Apps/Sandcastle2/index.html?id=imagery-assets-available-from-ion

RuntimeError: Ion.createResource does not support external imagery assets; use IonImageryProvider instead.
Error

The other assets look ok

[ggetz]

The Google Contour asset (id: 3830186) throws this error in http://localhost:8080/Apps/Sandcastle2/index.html?id=imagery-assets-available-from-ion

@lukemckinstry Thanks for catching that! This sandcastle example exposes an issue with how the cached endpoint responses were working. I have a fix and will also add unit tests.

The caching issue came up because addToolbarMenu is invoking the first function in the options list. I don't think this is expected as that is the behavior specified for addDefaultToolbarMenu, and the example accidentally creates the provider twice. Since that's out of scope of this PR, I will open a separate issue.

[lukemckinstry]

The IonResource additional Cesium client request headers and the retryCallback refactor look good 👍

[ggetz]

Thanks for the review @lukemckinstry! I just pushed up the caching fix and unit test updates.

Assuming the updates look good, this should be good to merge.