fw_update: Introduce AggregateUpdateManager

Description:
This commit introduces the `AggregateUpdateManager` class for handling
multiple firmware update sessions simultaneously. The
`AggregateUpdate

fw_update: Introduce AggregateUpdateManager

Description:
This commit introduces the `AggregateUpdateManager` class for handling
multiple firmware update sessions simultaneously. The
`AggregateUpdateManager` acts as a reverse proxy for PLDM messages,
routing them to the appropriate `UpdateManager` instance based on the
`instanceId`. This allows for concurrent firmware updates, improving
the efficiency and flexibility of the firmware update process.

Motivation:
We have introduced the `FirmwareInventory`/`FirmwareInventoryManager`
classes to manage D-Bus interfaces for firmware update, After that, we
would like to implement the `StartUpdate` method for `FirmwareInventory`
properly for the update process implementation[1], which
`AggregateUpdateManager` will help route the command to the specific
update sessions.

Details of the PLDM message reverse proxy:
By the implementation, different update session would be handled with
different `instanceId`s, which can help `UpdateManager`s to identify
whether the message is for them or not.
Whenever a PLDM response message is received, the flow that
the `AggregateUpdateManager` do:
1. Handle the message for existing update flow if the instance_id
(the pldm instance numbers) matches the update task which using the
existing update flow.
2. Traverse forward the message to each `ItemUpdateManager`
(implementation in the next patch) instances if there's no match in
step 1.
3. Return error message PLDM_FWUP_COMMAND_NOT_EXPECTED if no matches in
step 2.

[1]: https://gerrit.openbmc.org/c/openbmc/pldm/+/74774

Change-Id: Icfdb8d238121f9f44a624396e00b378e491ce652
Signed-off-by: Unive Tien <unive.tien.wiwynn@gmail.com>

show more ...