Expose configuration exceptions in scalafmt

[loveleif]

Read scalafmt configuration in a way that shows parsing errors.

Before this change invalid scalafmt configuration files would fail like this:

java.lang.reflect.InvocationTargetException
    ...
Caused by: java.util.NoSuchElementException: Either.right.value on Left
    at scala.util.Either$RightProjection.get(Either.scala:453
    ...

With this change any exceptions from scalafmt configuration parsing will be visible, for example:

java.lang.reflect.InvocationTargetException
    ...
Caused by: java.lang.IllegalStateException: Invalid fields: invalidScalaFmtConfigField
    at metaconfig.Configured.get(Configured.scala:11)
    ...

Resolves #837

[nedtwigg]

LGTM! Update all 3 changelogs, run spotlessApply, and I'd be happy to merge if all the tests still pass.

[nedtwigg]

Looks good except the tests are failing:

https://app.circleci.com/pipelines/github/diffplug/spotless/971/workflows/4841f147-d18e-432f-aa6e-ddd5ef26851a/jobs/5477

[loveleif]

the tests are failing

Sorry about that @nedtwigg, all green now :). By the way, thanks for all the hard work and making spotless available for anyone to use.

[nedtwigg]

Thanks for the contribution! Publishing is gunked up atm due to the jcenter sunset, but it'll get published by tomorrow.

[nedtwigg]

Released in plugin-maven 2.10.0 and plugin-gradle 5.12.0.