Move asset bundles into separate package

[brianjhanson]

Moves all of our existing asset bundle assets into a packages/craftcms-asset-bundles folder and @craftcms/asset-bundles subpackage. Much like #17924 this will allow us to split the build process between legacy and modern assets.

The number of changes makes GitHub's diff choke, so important things are:

• Register a new @assetBundles alias in the yii2-adapter that points to packages/craftcms-asset-bundles
• Replace all $sourcePaths with @assetBundles alias paths
• Move src and dist directories into packages/craftcms-asset-bundles

The build command is now build:bundles so you can build all the asset bundles with npm run build:bundles. Passing arguments gets a little more awkward unfortunately. To build a specific bundle you have to double up your -- so the command ends up being

npm run build:bundles -- -- --config-name=cp

This update unfortunately breaks the npm run serve ... commands because that currently relies on the front-end assets being colocated with the asset bundle class in order to resolve the dev server via the /which-asset route. I haven't figured out the best way around that, but it might just be to ignore it. Ideally we won't be doing substantial dev on any of these asset bundles going forward.

[brandonkelly]

@brianjhanson looks like this broke some asset bundle tests

[brianjhanson]

Found some issues with this. Closing so I can fix those up (and maybe reevaluate this approach)

[brandonkelly]

@brianjhanson I take it you’re happy with this now? Can you merge 6.x into this branch?