Encrypt/decrypt local file with key vault

**Is your feature request related to a problem? Please describe.**
No, it is not.

**Describe the solution you'd like**
I would like to be able to encrypt sensitive files with Azure Key Vault keys same way as for example google cloud cli does:
```
gcloud kms encrypt \
--location=[LOCATION] \
--keyring=[KEY_RING] \
--key=[KEY] \
--plaintext-file=[FILEPATH_AND_FILENAME_TO_ENCRYPT] \
--ciphertext-file=[FILEPATH_AND_FILENAME].enc
```
It would be very convinient and useful in daily work.

Example expected functionality behaviour:
```
az keyvault encrypt/decrypt
--key-id
--plaintext-file
--ciphertext-file
```

**Describe alternatives you've considered**
Google kms, hashicorp vault, ansible vault. I would like to have such feature in azure cli so my organization can be fully integrated with your services.

**Additional context**
There is such a behaviour in your service API covered:
https://docs.microsoft.com/en-us/rest/api/keyvault/encrypt