Updates for phosphor-debug-collector interfaces

[dhruvaraj S]

Proposing these updates to the existing phosphor-debug-collector DBus
interfaces to support dumps that get created and stored in the host
but notified and offloaded through BMC. looking for inputs from the
team.

Design doc: https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/28260

Update dump entry and add Notify method :
https://gerrit.openbmc-project.xyz/c/openbmc/phosphor-dbus-interfaces/+/28621

InitiateOffload method for the dump entry:
https://gerrit.openbmc-project.xyz/c/openbmc/phosphor-dbus-interfaces/+/28784/7

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Dhruvaraj S