[FLINK-7190] Activate checkstyle flink-java/*

[dawidwys]

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[dawidwys]

This is the last commit of series. It enables the stricter checkstyle. So should be merged last.

[greghogan]

What if we first split the suppressions files as with suppressions-runtime.xml? I think we could do this in one ticket for all of core, java, and optimizer.

[zentol]

@greghogan I agree, expanding the suppression files would be nice.

[zentol]

why are these excluded?

[dawidwys]

In NestedMethodAnalyzer:358-362, there is an intentional fall through which I would require a bit bigger refactoring to eliminate.

For the ExecutionEnvironment it was because we linked in javadoc to class from a package that flink-java does not depend on. I've checked the generated docs, and the links do not work nevertheless, so I removed the suppression and changed {@link to {@code.

[zentol]

The switch statements can be modified to be checkstyle compliant with few changes.
NestedMethodAnalyzer#naryOperation:

...
case INVOKESTATIC:
case INVOKESPECIAL:
case INVOKEVIRTUAL:
case INVOKEINTERFACE:
	isStatic = insn.getOpCoed() == INVOKESTATIC;
...

NestedMethodAnalyzer#copyOperation:

...
case DUP2_X2:
	if (isTagged(value) && tagged(value).isInput() && tagged(value).isCallByValue()) {
		return tagged(value).copy();
	} else {
		return super.copyOperation(insn, value);
	}
...

[zentol]

merging.