Write 64bit aligned IPC files

[jorgecarleitao]

This is a follow-up to https://lists.apache.org/thread/3wh51ml8zt00131fgmxj1lqg92dlgj41 and related to #1197

The gist is that, in my opinion, to read mmapped Arrow IPC files soundly, the buffers need to be written with a bit alignment consistent with their types. Currently the spec does not to support this. As such, i128 and i256 can't be soundly read via mmap with 64bit alignment, and no type other than i8 and u8 can be soundly read in 8bit aligned files.

We currently write files whose every buffer is 8bit aligned, which restricts zero-copy reading every type other than i8 and u8. This PR changes the write alignment to 64 bits. Note that this has virtually no impact to performance or file size, but is a requirement to mmap IPC files as per #1197 (and in general).

[codecov]

Codecov Report

Merging #1201 (435e9b4) into main (3f3febf) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1201   +/-   ##
=======================================
  Coverage   83.44%   83.44%           
=======================================
  Files         366      366           
  Lines       36697    36697           
=======================================
+ Hits        30621    30623    +2     
+ Misses       6076     6074    -2     

Impacted Files	Coverage Δ
src/io/ipc/write/common.rs	80.67% <100.00%> (ø)
src/io/ipc/write/common_async.rs	95.83% <100.00%> (ø)
src/io/ipc/write/common_sync.rs	94.73% <100.00%> (ø)
src/io/ipc/write/serialize.rs	96.15% <100.00%> (ø)
src/io/ipc/read/reader.rs	96.32% <0.00%> (-0.34%)	⬇️
src/array/binary/mod.rs	90.12% <0.00%> (+1.23%)	⬆️

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