[vmbase] Move RangeExt to vmbase for reuse

in both pvmfw and rialto.

No behavior change in this cl.

Bug: 284462758
Test: m pvmfw_img
Change-Id: Ifda7f4a2a08ebb6646c3c7e189a77c5ff3fe74a3
diff --git a/pvmfw/src/fdt.rs b/pvmfw/src/fdt.rs
index a68cf3a..ea002df 100644
--- a/pvmfw/src/fdt.rs
+++ b/pvmfw/src/fdt.rs
@@ -16,7 +16,6 @@
 
 use crate::bootargs::BootArgsIterator;
 use crate::cstr;
-use crate::helpers::RangeExt as _;
 use crate::helpers::GUEST_PAGE_SIZE;
 use crate::memory::MAX_ADDR;
 use crate::Box;
@@ -43,6 +42,7 @@
 use vmbase::layout::crosvm::MEM_START;
 use vmbase::memory::SIZE_4KB;
 use vmbase::util::flatten;
+use vmbase::util::RangeExt as _;
 
 /// Extract from /config the address range containing the pre-loaded kernel. Absence of /config is
 /// not an error.