MemoryManager: correct initial memory use and add mdebug command

- Use seL4_Untyped_Describe to get an accurate view of each
  UntypedMemory slab being managed; this makes mstats reflect
  rootserver allocations.
- Track memory allocated before we run as "overhead" (was meant to
  track fragmentation but was always zero).
- Add an "mdebug" command to describe each managed memory slab;
  this is useful to see whether the kernel's view of memory use is
  consistent with MemoryManager.

Change-Id: I53b2738c430ad3356ecd16a1cad29ca92dc74beb
GitOrigin-RevId: 2ad43f9b7760c722a6590ea049a3814c8dcccba7

apps/system/components/DebugConsole/kata-shell/src/lib.rs

@@ -124,6 +124,7 @@ pub fn repl<T: io::BufRead>(
         ("kvwrite",             kvwrite_command as CmdFn),
         ("install",             install_command as CmdFn),
         ("loglevel",            loglevel_command as CmdFn),
+        ("mdebug",              mdebug_command as CmdFn),
         ("mstats",              mstats_command as CmdFn),
         ("ps",                  ps_command as CmdFn),
         ("start",               start_command as CmdFn),
@@ -462,6 +463,18 @@ fn kvwrite_command(
     Ok(())
 }
 
+fn mdebug_command(
+    _args: &mut dyn Iterator<Item = &str>,
+    _input: &mut dyn io::BufRead,
+    output: &mut dyn io::Write,
+    _builtin_cpio: &[u8],
+) -> Result<(), CommandError> {
+    if let Err(status) = kata_memory_debug() {
+        writeln!(output, "stats failed: {:?}", status)?;
+    }
+    Ok(())
+}
+
 fn mstats(output: &mut dyn io::Write, stats: &MemoryManagerStats)
           -> Result<(), CommandError>
 {