azure_exporter modification

Metricss result after modification:

Metrics names in result:

azure_memory_percent_average
azure_resource_info
azure_storage_percent_average
azure_storage_used_bytes
node_cpu_average
node_filesystem_size_bytes
node_network_receive_bytes_total
node_network_transmit_bytes_total

I used config from attachment provided by Vadim here: https://jira.percona.com/browse/PMM-7500?focusedCommentId=278979&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-278979.

How to test (No FB needed): 
1. Download azure_metrics_exporter.zip from attachments.
2. Extract binary azure_metrics_exporter from zip above
3. Download azure-exporter-config.yml from attachments.
4. Fill Azure credentials in azure-exporter-config.yml instead "XXX"
4. Run command: azure_metrics_exporter --config.file="azure-exporter-config.yml"
5. Open http://127.0.0.1:9276/metrics and check that these metrics are presented:
    - azure_memory_percent_average
    - azure_resource_info
    - azure_storage_percent_average
    - azure_storage_used_bytes
    - node_cpu_average
    - node_filesystem_size_bytes
    - node_network_receive_bytes_total
    - node_network_transmit_bytes_total

Suggested implementation:
1. Fork https://github.com/RobustPerception/azure_metrics_exporter
2. Modify metrics names cpu_percent_percent_average, network_bytes_egress_bytes_average, network_bytes_ingress_bytes_average, storage_limit_bytes_average to RDS naming.
3. Add prefix azure_ before these metrics: storage_used_bytes_average, storage_percent_percent_average, memory_percent_percent_average and remove double percent from them.

It's required to modify default metric names in order to have equal metrics with other exporters (node_exporter, rds_exporter).

Next metrics are unique. No similar metrics are collected by other exporters.
IMHO it would be convenient to add prefix azure_ and remove double percent word.