KfComponentsHolder cleanup

Cleanup of KfComponentsHolder.
It became a bit more urgent due to changes introduced by thread-safety.
Restore the timing performance of the Chi2MeasurementEstimator (still pretty deceiving though).

No regression expected, no regression observed
right.
Unfortunately this code is still using CLHEP matrix and standard KF algebra with H (few line above) and this very routine is returning H (that the holder recreates on the fly.

In any case Alignment responsibles said that this (and related classes) will be reimplemented "soon"