feat: Migrate layer data event sample

[willum070]

This PR does the following things:

• Migrates the layer-data-event sample into js-api-samples.
• Updates layer-data-event to use gmp-map and dynamic library loading.
• Updates layer-data-event to use a local JSON asset rather than linking to a bucket (the bucket is gone now, hence the PR).

[snippet-bot]

Here is the summary of changes.

You are about to add 4 region tags.

• samples/layer-data-event/index.html:7, tag maps_layer_data_event
• samples/layer-data-event/index.ts:7, tag maps_layer_data_event
• samples/layer-data-event/index.ts:30, tag maps_layer_data_event_snippet
• samples/layer-data-event/style.css:6, tag maps_layer_data_event

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