Add basic converter for macros plantuml and plantumlrender

The goal of this issue is to implement a converter that would convert macros plantuml and plantumlrender into XWiki's plantuml macro, with eventual parameters.

Documentation for the two macros :

• plantuml : https://avono-support.atlassian.net/wiki/spaces/PUML/pages/9699367/Macro+plantuml
• plantumlrender : https://avono-support.atlassian.net/wiki/spaces/PUML/pages/33816578/Macro+plantumlrender+and+flowchartrender

The particularity of the plantumlrender macro is that its content can also contain Confluence markup, and Confluence macros. For now, this conversion is out of scope.