* Upgrade to Checkstyle `7.1`
* Relax `RequireThis` rule a bit. Right now it does the effort only in case of overlapping. See https://github.com/checkstyle/checkstyle/issues/2362 for more info
* Enable some annotation rules and provide fixes for violations
* Enable `tabs indents` rule. This was the biggest fix in this PR
* Resolve `TODO` in the `MessagingMethodInvokerHelper` and fix tests to meet `IllegalStateException` now
Remain Checkstyle version `6.16.1` and reinstate `RequireThis` rule
The latest Checkstyle has a bug with local scope variables if they have the same names as property.
Revert some literals splitting
Fix some line length exceeding and code style
12fb590b95