os.linux: Move buildThreadAttributeName() methods to Attributes interface

os.linux: Move buildThreadAttributeName() methods to Attributes interface

The method buildThreadAttributeName() and its counterpart
parseThreadAttributeName() are related to attributes tree
walking, and not to the event handlers themselves. Move them
to the Attributes interface.

Change-Id: Ide7b7154cfff0e12f74eda7a64f3545114b93e80
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/70298