[spring index] replace EnhancedSymbolInformation for beans with new spring index information

[martinlippert]

The enhanced symbol information for BeansSymbolAddOnInformation doesn't seem to be necessary anymore given the new spring index that provides the same information, so we should remove BeansSymbolAddOnInformation and use the new spring index instead we necessary.

[martinlippert]

This is used by the XML bean ref content-assist and definition providers, so a prerequisite of this is to integrate the XML symbol scanning into the new bean index.

[martinlippert]

First steps: 24492fe, d81feb0, 9bffd04, 2e7db46, 7a83c07