[INTERNAL] EventProvider: refactor fireEvent loop and array checks
[INTERNAL] EventProvider: refactor fireEvent loop and array checks

 - consistently use Array.isArray for array checks
 - use only a single for-loop to notify an array of listeners  
 - borrow event object even more lazily
 - fix some minor JSDoc issue
 
Change-Id: I252307b244c016e7b3ccbbe65a44f82106ebe0fc

SQCLabs/openui5,SQCLabs/openui5,olirogers/openui5,nzamani/openui5,nzamani/openui5,olirogers/openui5,SAP/openui5,SQCLabs/openui5,SAP/openui5,cschuff/openui5,cschuff/openui5,nzamani/openui5,olirogers/openui5,cschuff/openui5,SAP/openui5,SAP/openui5