1. DebugAgentLib will install reserved vector table to persist vectors.

1. DebugAgentLib will install reserved vector table to persist vectors.
2. Update PeCoffExtraActionLib to detect if debug agent initialized or not by checking each IDT entry instead of whole IDT table.

Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14886 6f19259b-4bc3-4df7-8a09-765794883524