Scalafmt introduction post work

[errt]

Some more changes in the wake of removing Scalariform in favor of Scalafmt

[maximilianruesch]

We can probably address some concerns from https://github.com/opalj/opal/pull/182#pullrequestreview-1828147803 using the indentOperator.excludeRegex from https://scalameta.org/scalafmt/docs/configuration.html#indentoperator with an impossible regex like (?!x)x which would effectively evaluate indentOperator.exemptScope to None.

[errt]

Not sure from reading the documentation, but isn't exemptScope stronger than excludeRegex? We can still try, it should maybe indent some boolean expressions better, as the default for excludeRegex is && and ||.

[maximilianruesch]

Imo they can be made the same strength:

• exemptScope: "This parameter determines when an infix operator can be exempted from applying continuation indentation."
• excludeRegex "Defines a regular expression for excluded infix operators. If an eligible operator matches, it will not be indented."

When "continuation indentation" and "it will be indented" mean the same, setting an impossible regex should just emulate exemptScope=None.

Regardless of how strong it is, imo worth a try.

[errt]

Works, but I put it in another PR: #188