VOLUME.CHANGE.DISK.OFFERING does not generate VOLUME.RESIZE usage event when volume size remains unchanged

### problem

When a volume's disk offering is changed to another offering with the same size, CloudStack does not emit a VOLUME.RESIZE event in cloud.usage_event

### versions

ACS version is 4.19.1.1

### The steps to reproduce the bug

Steps to reproduce:

Case 1 - Resized volume, same capacity after disk offering change

- Create Volume A using Disk Offering A with an initial size of 300 GB.
- Resize the volume to 400 GB.
- Change the disk offering from Disk Offering A to Disk Offering B, while keeping the volume size at 400 GB.
Result: The disk offering change completed successfully, but no new VOLUME.RESIZE usage event was generated.

Case 2 - Fixed-size disk offerings with the same capacity

- Create Volume A using Disk Offering A with a fixed size of 400 GB.
- Change the disk offering to Disk Offering B, which also has a fixed size of 400 GB.
Result: The disk offering was updated successfully, but no VOLUME.RESIZE usage event was generated.

Case 3 - Custom-size disk offerings with the same capacity

- Create Volume A using Disk Offering A with a custom size of 400 GB.
- Change the disk offering to Disk Offering B, while keeping the volume size at 400 GB.
Result: The disk offering change completed successfully, however no VOLUME.RESIZE usage event was generated.

Case 4 - Disk offering change with a different volume size

- Create Volume A using Disk Offering A with a size of 300 GB.
- Change the volume to Disk Offering B and increase the volume size to 400 GB as part of the same operation.
Result: CloudStack generated both the VOLUME.CHANGE.DISK.OFFERING event and a new VOLUME.RESIZE usage event, and the billing information was updated correctly.

Actual behaviour:

CloudStack generates a `VOLUME.CHANGE.DISK.OFFERING` event in the `cloud.event` table, confirming that the operation completed successfully.

However, no new `VOLUME.RESIZE` entry is created in the `cloud.usage_event` table.

As a result, the usage records continue to reference the previous disk offering, and downstream billing continues to use the old offering information.

Additional observations:

- The volume is successfully updated to Disk Offering B.
- The volume size remains unchanged.
- The latest `cloud.usage_event` entry still references Disk Offering A.
- Billing data derived from `cloud.usage_event` therefore continues to report the previous offering.

### What to do about it?

Expected behaviour:

A usage event should be generated (or the existing usage information updated) so that the billing system reflects the new disk offering, even though the volume size has not changed.

Rastreie o caminho de alteração da oferta de disco e o tratamento de VOLUME.CHANGE.DISK.OFFERING e VOLUME.RESIZE em cloud.event e cloud.usage_event. Reproduza primeiro os casos com o mesmo tamanho e, em seguida, verifique se a alteração da oferta registra o uso associado à nova oferta mesmo quando o tamanho do volume permanece inalterado.

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