[Fleet] Split bulk delete into chunks to avoid high memory consumption

[xcrzx]

Related to: #187969

Summary

For packages with a large number of assets, when performing reinstall or upgrade, we need to limit bulk delete requests to a fixed number of saved objects.

Currently, the bulk delete method is called with all package assets:

await savedObjectsClient.bulkDelete(assetsToDelete, { namespace });

This means that significant request and response objects will be created and stored in memory at the same time before being garbage collected. Splitting that work into smaller chunks can reduce memory pressure:

const chunks = chunk(assetsToDelete, MAX_ASSETS_TO_DELETE);

for (const assetsChunk of chunks) {
  await savedObjectsClient.bulkDelete(assetsChunk, { namespace });
}

This way, completed bulk delete requests with smaller payloads and responses can be garbage collected along the package removal process, leading to smaller overall memory consumption.

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