MFC r258220, r258251:
Implement automatic live resize support for GEOM MULTIPATH class.

In "manual" mode just automatically resize provider in any direction.
In "automatic" mode allow growth (with new metadata write); in case of
shrinking check if there is already valid metadata found at the new
location. This should allow easy transparent recovery if first resize
was done by mistake.

While there, unify metadata write code and fix minor memory leak.

MFC r258220, r258251:
Implement automatic live resize support for GEOM MULTIPATH class.

In "manual" mode just automatically resize provider in any direction.
In "automatic" mode allow growth (with new metadata write); in case of
shrinking check if there is already valid metadata found at the new
location. This should allow easy transparent recovery if first resize
was done by mistake.

While there, unify metadata write code and fix minor memory leak.