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ARROW-5579: [Java] Shade flatbuffers

- Merge the format package into the vector package
- shade flatbuffers in vector
- create missing wrappers to avoid direct flatbuffer dependencies in flight

[] Possibly add unit tests to cover new functions/classes.

@pravindra @tianchen92 please take a look, I think this is the only reasonable way to shade flatbuffers.  I don't know if there was any particular reason that format and vector where separate but I think  it makes it very difficult to shade if we don't take this approach.

Closes #4701 from emkornfield/shade2 and squashes the following commits:

4269ce8 <Micah Kornfield> add comment
d196772 <Micah Kornfield> rename getType
45fad2a <Micah Kornfield> address CR feedback
f5a3a70 <Micah Kornfield> centralize serialization code in the serializer
9b54c6e <Micah Kornfield> ArrowMessageHeader->ArrowMessageMetadata
8daeca4 <Micah Kornfield> remove extra whitespace
90eebb3 <Micah Kornfield> address feedback part 1
38fabe8 <Micah Kornfield> Add shading, cleanup depedencies and CI for shaded artifacts
11f9303 <Micah Kornfield> Refactor java files so all flatbuffers are wrapped in vector

Authored-by: Micah Kornfield <emkornfield@gmail.com>
Signed-off-by: Bryan Cutler <cutlerb@gmail.com>