Fix: Correctly support Intellij 193+

[dansanduleac]

Before this PR

Loading CodeStyleManager programmatically in a way that is not (really) supported in IntelliJ builds 193 and up.
It kind of works, but keeps throwing a lot of errors.

After this PR

==COMMIT_MSG==
Get rid of constant error in new Intellij 193 by replacing CodeStyleManager via a plugin.xml-declared service override, rather than programmatically using internal APIs.
==COMMIT_MSG==

Got the idea here: google/google-java-format#404 (comment)

Fixes #50

Possible downsides?

• not entirely sure this works on previous versions, need to double check works at least on 191.5849.21
• feels weird to have to reference the intellij default Impl class directly, but don't know how to refer to the original default as defined in IntelliJ's META-INF/LangExtensions.xml

[dansanduleac]

I think there might be a better way of hooking into CodeStyleManager than replacing it...

The impl seems to have logic that delegates to an ExternalFormatProcessor, although this logic has only existed since 191.4212.41:

• https://github.com/JetBrains/intellij-community/blob/9c931cdc0cb5a6d4093ecf4d79b0c1305d4ae512/platform/lang-impl/src/com/intellij/psi/impl/source/codeStyle/CodeStyleManagerImpl.java#L297-L299
• https://github.com/JetBrains/intellij-community/blob/9c931cdc0cb5a6d4093ecf4d79b0c1305d4ae512/platform/lang-impl/src/com/intellij/psi/impl/source/codeStyle/CodeStyleManagerImpl.java#L84-L86

[dansanduleac]

Update: ExternalFormatProcessor doesn't always get called, which means we can't use it to provide the same functionality, sadly. For instance, it gets called when reformatting a snippet via Command+Shift+ENTER, but not when reformatting a selected chunk / the whole file via Command+Alt+L.

[CRogers]

Approved modulo manual testing

[iamdanfox]

Smoke-tested and was still able to format files on my IntelliJ!

IntelliJ IDEA 2019.2.1 (Community Edition)
Build #IC-192.6262.58, built on August 20, 2019
Runtime version: 11.0.3+12-b304.39 x86_64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.14.6
GC: ParNew, ConcurrentMarkSweep
Memory: 1933M
Cores: 12
Registry: 
Non-Bundled Plugins: EclipseCodeFormatter, org.intellij.scala, palantir-java-format