Revised naming for prototype inner beans to avoid excessive unique name calculation

Restored original singleton-only adaptInnerBeanName behavior, avoiding endless unique name calculation for every single prototype instance. Non-named inner BeanDefinition objects now suffixed with an identity hex code analogous to non-named XML bean definitions, largely avoiding naming collisions to begin with. After SPR-11246, post-processors can deal with unstable classes per bean name, so occasional collisions aren't a hard problem anymore.

Issue: SPR-11545
(cherry picked from commit 5308b3e)
BufferedImageHttpMessageConverter ignores empty MIME types

Issue: SPR-11581
(cherry picked from commit 90e3dbb)
Consistently applied appropriate ByteArrayOutputStream initial capacities across the codebase

Issue: SPR-11594
(cherry picked from commit dd7f54c)
DispatcherServlet logs request URI in encoded form only

Issue: SPR-11591
(cherry picked from commit 465ca24)
Polishing