Revert "BaseTools:BaseTools supports to the driver combination."

Revert "BaseTools:BaseTools supports to the driver combination."

This reverts commit 838bc257bae3f9fc6723f41f3980f6cfbedb77e5.
After further evaluation, there are the unclear behavior in for the
driver combination feature. To not impact Q1 stable tag, remove it first.
1. If the drivers to be combined have the different PCD or library instance
   setting, build should not combine them and report build break. But this
   commit doesn't consider this case.
2. When start the sub driver fail, continue to start other sub driver. This
   behavior is required to be clarifed in build spec.
3. Unload the sub driver when the combined driver start fail. This case need
   to call the sub driver unload function for the driver start fail only.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>