fs: remove thread_local storage

If we are not zero-filling containers then the overhead of allocating them
on each use is negligible.  The effect that the thread_local containers
were having on RAM usage was very non-negligible.

Use dynamic containers (members or stack objects) for better control
of object lifetimes and much lower peak RAM usage.  They're a tiny bit
faster, too.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/fs.h

@@ -95,6 +95,7 @@ namespace crucible {
 			iterator m_end = nullptr;
 		friend struct BtrfsIoctlLogicalInoArgs;
 		} m_iors;
+		BtrfsDataContainer m_container;
 	};
 
 	ostream & operator<<(ostream &os, const BtrfsIoctlLogicalInoArgs &p);