Description of problem:
Migration metrics names are inconsistent.
The following metrics :
kubevirt_migrate_vmi_data_processed_bytes
kubevirt_migrate_vmi_data_remaining_bytes
kubevirt_migrate_vmi_dirty_memory_rate_bytes
kubevirt_migrate_vmi_disk_transfer_rate_bytes
kubevirt_migrate_vmi_memory_transfer_rate_bytes

Have a "kubevirt_migrate_vmi" prefix, while the following metrics:

kubevirt_vmi_migrations_failed
kubevirt_vmi_migrations_succeeded
kubevirt_vmi_migrations_pending
kubevirt_vmi_migrations_running
kubevirt_vmi_migrations_scheduling

Have a "kubevirt_vmi_migrations_" prefix.
All these metrics should have the same prefix.

We may want to have it as "kubevirt_vmi_migration_" where we use the singular form of "migration".

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. Search for vmi migration metric.
2.
3.

Actual results:
Not all vmi migration metrics have the same prefix

Expected results:
All vmi migration metrics should have the same prefix.

Additional info: