Add an option to mount tmp on a Persistent Volume (PV)

[vfiset]

Description
Since meilisearch relies so much on tmp files for performance, there should be an option to mount /tmp on a PV

Basic example
Spin a meilisearch instance on a k8s node with a limited amount of disk space add use it.

Then you'll eventually get to this point:

/meili_data $ du -sh /tmp/.tmppQOJrc
20.2G   /tmp/.tmppQOJrc
/meili_data $ 

Then this point:

message: "The node was low on resource: ephemeral-storage. Threshold quantity: XX, available: XX. Container meilisearch was using XX, request is 0, has larger consumption of ephemeral-storage. Container sidecar was using XX, request is 0, has larger consumption of ephemeral-storage. "

For the record, our node has a small 60G disk.

Other
Yes we can add a request for ephemeral storage but we'll push the problem to some other pods that will be evicted since meilisearch is such a heavy user.