XRENDERING-654: Add rendering entry points for the PAGE_ATTACHMENT entity type

...i/office/viewer/internal/DefaultOfficeResourceViewer.java

...ldcore/src/main/java/com/xpn/xwiki/doc/XWikiDocument.java

...XWikiPageAttachmentContentInputSourceReferenceParser.java

...atform-oldcore/src/main/resources/META-INF/components.txt

...iPageAttachmentContentInputSourceReferenceParserTest.java

...g/xwiki/refactoring/internal/DefaultReferenceRenamer.java

.../java/org/xwiki/rendering/internal/parser/LinkParser.java

...ternal/renderer/XWikiPageAttachmentURILabelGenerator.java

...geAttachmentResourceReferenceEntityReferenceResolver.java

...endering-xwiki/src/main/resources/META-INF/components.txt

...tachmentResourceReferenceEntityReferenceResolverTest.java