Update mongo in K8S configs to a supported version

[kszicsillag]

Is your feature request related to a problem? Please describe.
Mongo DB version referenced in K8S YAMLs e.g.

aks-store-demo/aks-store-all-in-one.yaml

Line 20 in 1b7ba07

image: mcr.microsoft.com/mirror/docker/library/mongo:4.2

is deprecated. The old version causes problems with liveness probing, see #197.

Describe the solution you'd like
Update mongo image reference to a supported version and adjust requests & limits (newer version may require more resources)

Describe alternatives you've considered

Additional context