[Routing] made RouteCompilerInterface::compile static
merged branch Tobion/static-compile (PR #6491)

This PR was squashed before being merged into the master branch (closes #6491).

Commits
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5d264ce [Routing] made RouteCompilerInterface::compile static

Discussion
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[Routing] made RouteCompilerInterface::compile static

bc break: yes but probably nobody affected

It makes much more sense that the compile method is static because having instances of a compiler is strange. Also the compiler could not use DI or anything anyway as the `Route` class was instantiating compiler instances itself and was assuming there are no constructor arguments.