The cleanup multi-font related code in the XFontPeer

This change is the part of my effort to clean up the native initialization code in awt/2d. Initially, I have dropped the native code inside initIds() which was unused. Now I tried to check is the code inside initIDs() is used for the meaningful purpose.

I found that XFontPeer.initIds() uses XFontPeer.xfsname field which is always null, so in this fix, I have dropped the field itself, the initIds, the methods which depend on this field, and methods which calls methods which depends on this field, etc.