6871111: G1: remove the concurrent overhead tracker Summary: Removing the concurrent overhead tracker from G1, along with the GC overhead reporter and the G1AccountConcurrentOverhead (both of which rely on the the concurrent overhead tracker). Reviewed-by: iveresov, johnc

These files are generated from docs/technotes/tools pages in the
jdk/pubs subspace of the jdk workspace (adjacent to jdk/j2se).