Add support for --allow-downgrades flag in init container

[Vegoo89]

Is your feature request related to a problem?/Why is this needed
Currently I am experiencing issue described in Azure/azure-storage-fuse#1639 and I have to downgrade blobfuse2 to version 2.3.0 on all my AKS nodes until solution is found

Describe the solution you'd like in detail
I would like --allow-downgrades parameter to be setable as Helm chart value for blobfuse and blobfuse2 installation via install-blobfuse-proxy init container

Describe alternatives you've considered
Right now I am settings node.blobfuseProxy.blobfuse2Version to 2.3.0 --allow-downgrades which works, but it can be done in clearer way with minimal effort

Additional context
N/A