Enable random access when opening a SeekableByteChannel or FileChannel

[arouel]

Description of changes:

• Enable simultaneous READ and WRITE support when opening a SeekableByteChannel (or FileChannel).
• Enable random access to the temporarily cached S3 file, so that we can seek to a particular position, and read from or write to that.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[markjschreiber]

Thanks for this contribution. It looks like the CI check failed during integration testing with:

FileChannel$open* should read and write on S3 > open with READ and WRITE is supported FAILED
    java.nio.file.NoSuchFileException at FileChannelTest.java:41

FileChannel$open* should read and write on S3 > open with CREATE and WRITE is supported FAILED
    java.util.concurrent.CompletionException at FileChannelTest.java:67
        Caused by: software.amazon.awssdk.core.exception.SdkClientException at FileChannelTest.java:67

Can you take a look? Let me know if you need help.

[arouel]

The test failures are caused by missing AWS credentials while either downloading or uploading the temporary file. I wonder why, because the test setup works. I'm surprised that the test cases in FilesWriteTest work, but the newly added testes don't due to credentials.

[arouel]

@markjschreiber I found the problem and fixed it. Please have a look at line 838 to 840 in S3FileSystemProvider. Calling on the path toUri and then resolving the FileSystem didn't work. This can be avoided by resolving the file system directly from the incoming S3Path.

[markjschreiber]

Not sure if you saw the comment on adding usnit tests for the new methods in S3WritableByteChannel? With those I believe we can merge this PR.

[markjschreiber]

Updating this PR to merge in other changes. Hopefully this will make it easier to merge when you add unit tests

[arouel]

I've added the unit tests as requested. Let me know if it needs some changes.

[markjschreiber]

Nice addition! Thanks.