v0.28: Dumps are now async tasks

[guimachiavelli]

With v0.28, dumps are now handled the same as other Tasks (e.g. add documents, update settings). However, dumps do have priority in the queue and are bumped to the top of the task queue when requested—if a task is being processed, that request is finished and the dump begins immediately afterward.

References

Issue on core: meilisearch/meilisearch#2371
Spec: meilisearch/specifications#139
SME: @MarinPostma, @curquiza

[maryamsulemani97]

@dichotommy Should I remove dumps.get as part of #1738?