Supress run_highs clock calls when time_limit is infinite

[jajhall]

The basic HiGHS timing for output and timeout checking has no meaningful overhead, but the timing calls for development profiling have c.4% overhead so should be off by default

[jajhall]

Already implemented

[jajhall]

Reading the run_highs clock to check for time-out is pointless when time_limit is kHighsInf and is reported to have a meaningful overhead, so suppress it.

[jajhall]

Closed by #1941