Update junit to junit5 and checkstyle to checkstyle 8

[snuyanzin]

The PR

1. updates dependencies
   checkstyle 7.8.2 => 8.16
   junit 4.12 => 5.3.2
   maven-assembly-plugin 3.0.0 => 3.1.1
   maven-dependency-plugin 2.10 => 3.1.1
   maven-enforcer-plugin 3.0.0-M1 => 3.0.0-M2
   maven-jar-plugin 3.0.0 => 3.1.1
2. introduces dependency to hamcrest as it is not embedded into junit5
3. moves SuppressionCommentFilter, SuppressionCommentFilter, SuppressWithNearbyCommentFilter under TreeWalker and removes FileContentsHolder as it is declared in checkstyle's RN http://checkstyle.sourceforge.net/releasenotes.html#Release_8.2
4. Updates usage of assertEquals as its signature changed (message started to be the last argument)
5. Use assertArrayEquals where it is possible
6. Use Files.createTempFile for temporary files as junit5 has limited support of temporary files

fixes #265

[julianhyde]

Merged as 3ef84fa, fixes #265.