Use uppercase for classpath-related static final field names

[sdeleuze]

In order to ensure consistency across the codebase and communicate properly that static final fields of type String or Class<?> are inlinable constants as defined in the Spring code style, this issue intends to rename such fields named like fooPresent to FOO_PRESENT.

Those fields are not part of Spring public API, except org.springframework.web.servlet.support.RequestContext#jstPresent which will be renamed to JSTL_PRESENT as part of Spring Framework 7 new major.