core: Removed deprecated StringBuilderCompat class

Remove the deprecated StringBuilderCompat class and replaced all usages
to use the standard StringBuilder, in the single classes that special
methods were used, the methods were extracted to the using class itself

Change-Id: I5192154dc008c18c4169020c8bfe71946c3c8716
Signed-off-by: Tal Nisan <tnisan@redhat.com>