New image tile source

[tschaub]

This is a new version of the changes in #14262. I needed to squash the commits to deal with all the conflicts in the past couple years.

This adds a new ol/source/ImageTile.js module that is intended to replace the following:

• ol/source/UrlTile.js
• ol/source/TileImage.js
• ol/source/XYZ.js
• ol/ImageTile.js
• ol/tileurlfunction.js

The new source accepts a url option that can be a single URL template, an array of URL templates, or a function that returns a URL. The resulting loader returns a promise that creates an image, sets its src, and resolves when the image loads. For more complex image loading scenarios, the source can be passed a loader option.

Since we have some breaking changes already merged in, I thought it could make sense to deprecate a few things and merge this in.

When we are ready to remove ol/source/TileImage.js, we can update the the 9 sources that extend TileImage to instead extend the ImageTile source. This will be a breaking change since some of the options no longer make sense (tileLoadFunction, urls, cacheSize).

[github-actions]

📦 Preview the website for this branch here: https://deploy-preview-15568--ol-site.netlify.app/.

[thomasmoelhave]

Maybe it's too early for feedback here, if so I apologize :).

It's exciting to see some change in this part of OpenLayers. I tried comparing the two "WMTS Tile Transistions" examples.

current version
this PR

Here's a video showing difference. First the version in this MR, and second the version from openlayers.org.

Screencast.from.05-14-2024.02.34.03.PM.webm

I feel the new version has some problems compared to the current version, in particular in terms of added flickering.

This example, introduced in #4389 was made primarily to test how the interim tiles work, and how we render the most recently received tiles while waiting for updated images corresponding to a dimension change.