blockdev-mirror: More efficient handling of sparse mirrors

Merge Request Required Information

Summary of Changes

Fix block mirroring to have more control over the allocation patterns of the destination (whether a user wants it to be sparse or fully allocated), along with a knob the user can set to optimize if the destination reads as zero but QEMU can't efficiently discover that fact.

Approved Development Ticket(s)

All submissions to CentOS Stream must reference a ticket in Red Hat Jira.

Jira: RHEL-82906

Jira: RHEL-83015

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List tickets each on their own line of this description using the format "Resolves: RHEL-76229", "Related: RHEL-76229" or "Reverts: RHEL-76229", as appropriate.