tmf.common: Add a data size and speed formatter

tmf.common: Add a data size and speed formatter

This allows to format numbers representing sizes and speeds in bytes[/s] to
the closest thousand with 3 decimals. Format also includes the units.

This patch updates the kernel memory usage view to use this formatter.

Change-Id: I637f9e408d75f6a3948169d6fde5e8da596b17ce
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/70287
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>