Check for http enabled storage accounts in AzureFS IT tests

Add AzureFS standalone E2E test

This closes #7384.

The flip6 build profile only runs the Flip-6 related test cases. Moreover,
all Flip-6 related test cases are excluded when not running the flip6 build
profile. This should reduce testing time when adding more and more Flip-6
test cases.

Include flink-test-utils-junit in all submodules to make the Category marker interfaces Flip6 and OldAndFlip6 available

This closes #4889.

[FLINK-8373] [core, hdfs] Ensure consistent semantics of FileSystem.mkdirs() across file system implementations.

This closes #5042.

- do not shade everything, especially not JDK classes!
-> instead define include patterns explicitly
- do not shade core Flink classes (only those imported from flink-hadoop-fs)
- hack around Hadoop loading (unshaded/non-relocated) classes based on names in
  the core-default.xml by overwriting the Configuration class (we may need to
  extend this for the mapred-default.xml and hdfs-defaults.xml):
-> provide a core-default-shaded.xml file with shaded class names and copy and
  adapt the Configuration class of the respective Hadoop version to load this
  file instead of core-default.xml.

Add checkstyle suppression pattern for the Hadoop Configuration classes

Also fix the (integration) tests not working because they tried to load the
relocated classes which are apparently not available there

Remove minimizeJar from shading of flink-s3-fs-presto because this was
causing "java.lang.ClassNotFoundException:
org.apache.flink.fs.s3presto.shaded.org.apache.commons.logging.impl.LogFactoryImpl"
since these classes are not statically imported and thus removed when
minimizing.

Fix s3-fs-presto not shading org.HdrHistogram

Fix log4j being relocated in the S3 fs implementations

Add shading checks to travis

This adds two implementations of a file system that write to S3.
Both are not actual re-implementations but wrap other implementations and shade dependencies.

(1) A wrapper around Hadoop's s3a file system. By pulling a smaller dependency tree and
    shading all dependencies away, this keeps the appearance of Flink being Hadoop-free,
    from a dependency perspective.

(2) The second S3 file system is from the Presto Project.
    Initial simple tests seem to indicate that it responds slightly faster
    and in a bit more lightweight manner to write/read/list requests, compared
    to the Hadoop s3a FS, but it has some semantical differences.

This closes #4818