build: Added WhitespaceAround and WhitespaceAfter rules to Checkstyle config

[Oliver-Loeffler]

Issue

Actually I was wrong with adding the OperatorWrap check as solution to test for leading/trailing spaces around operators.
OperatorWrap only ensures that we get the following pattern when line wraps are needed: The proper solution here is to use WhitespaceAround and WhitespaceAfter.

Checkstyle will complain this one using OperatorWrap:

        int d = c +
                10;

It will permit:

        int d = c
                + 10;

To check if e.g. spaces are placed around operators or lambdas or behind a comma, following 2 rules apply.
Please test so we can find a suitable configuration.

        <module name="WhitespaceAfter"/>
        <module name="WhitespaceAround"/>

This setup ensures that we actually get the whitespaces around lambdas, around operators +, ||, etc and it ensures that e.g. missing whitespace after , or { is detected.

WhitespaceAround: https://checkstyle.org/config_whitespace.html#WhitespaceAround
WhitespaceAfter: https://checkstyle.org/config_whitespace.html#WhitespaceAfter

Fixes #620

Progress

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