vm_phys_early_alloc_ex*(): Introduce VM_PHYS_EAF_ADDR_BOUNDARIES_FIRST

[olce]

Summary

This new flag allows to specify a preference for chunks at boundaries in
phys_avail[].

When present, the vm_phys_early_alloc_ex*() functions first behave as if
VM_PHYS_EAF_ADDR_BOUNDARIES had been specified and other conflicting
flags or arguments ('chunk_start_idx') not present, but if that fails,
they will then fallback to an allocation with the other passed flags and
parameters.

[olce]

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