ARROW-5934: [Python] Bundle arrow's LICENSE with the wheels

Setuptools can handle multiple license files, but they get overwritten because of the same naming, so move the content python/LICENSE.txt to the top level LICENSE.txt.  I've investigated a solution to concatenate these, but it would require to extend multiple distutils/setuptools/wheel commands in a really error-prone fashion.
- Distribute the top level LICENSE.txt file with the wheels
- Distribute the top level LICENSE.txt with the source distribution, however `python setup.py bdist` leaves LICENSE.txt file as a garbage in the rebository, it cannot cleanup properly probably because the relative directory reference.

Add 3rdparty licenses because of the static-linkage in the wheels:
- lz4: https://github.com/lz4/lz4/blob/dev/lib/LICENSE#L11-L13
- zstd: https://github.com/facebook/zstd/blob/dev/LICENSE#L13-L15
- rapidjson: because of transitive dependencies https://github.com/Tencent/rapidjson/blob/master/license.txt#L21
- uriparser: https://github.com/uriparser/uriparser/blob/master/COPYING#L15-L18
- double-conversion: https://github.com/google/double-conversion/blob/3f9cd30e1bca91c0a036ad8b2b7eb8e2d2290dd2/LICENSE#L8-L11
- snappy: https://github.com/google/snappy/blob/master/COPYING#L10-L13
- brotli: https://github.com/google/brotli/blob/master/LICENSE#L10
- jemalloc is already added
- protobuf is already added
- gflags: https://github.com/gflags/gflags/blob/master/COPYING.txt#L10-L13
- c-ares: https://github.com/c-ares/c-ares/blob/master/LICENSE.md
- glog: https://github.com/google/glog/blob/master/COPYING#L10-L13
- boost is already added
- flatbuffers is already added
- grpc: https://github.com/grpc/grpc/blob/master/NOTICE.txt
- gtest: do we redistribute any binaries from it?
- gbenchmark: do we redistribute any binaries from it?
- apache thrift added
- apache orc added
- zlip is redistributed as a shared library with all wheels (in the future we should switch to static linkage)
- openssl and libcrypto is redistributed as shared libraries with the windows wheels, so added the openssl license preceding version 3

bzip2 doesn't require to include its license with binary redistributions: https://github.com/asimonov-im/bzip2/blob/master/LICENSE

Authored-by: Krisztián Szűcs <[email protected]>
Signed-off-by: Wes McKinney <[email protected]>

Closes apache#4880 from kszucs/wheel-license and squashes the following commits:

b839964 <Krisztián Szűcs> openssl
f220c66 <Krisztián Szűcs> zlib
064444d <Krisztián Szűcs> distribute notice as well
bee17ac <Krisztián Szűcs> orc notice
25f738c <Krisztián Szűcs> Thrift and ORC
54a643b <Krisztián Szűcs> grpc
baa7796 <Krisztián Szűcs> glog
0a3070e <Krisztián Szűcs> c-ares
749574f <Krisztián Szűcs> gflags
52d7e19 <Krisztián Szűcs> typo
0697927 <Krisztián Szűcs> brotli
51b9264 <Krisztián Szűcs> re2
5418a0e <Krisztián Szűcs> snappy and double-conversion
5647ab9 <Krisztián Szűcs> lz4 and rapidjson
29fa7e0 <Krisztián Szűcs> wheel licensing

Author: kszucs