ARROW-7726: [CI] [C++] Use boost binaries on Windows GHA build
ARROW-7726: [CI] [C++] Use boost binaries on Windows GHA build

The binaries are installed using Chocolatey, which takes a bit of time (it's a 2+GB install...), but less so than recompiling Boost from scratch during the CMake build.

[skip appveyor]

Closes #6325 from pitrou/ARROW-7726-download-boost-gha and squashes the following commits:

e877622b9 <Antoine Pitrou> Revert "Try a more flexible way of finding Boost"
eb5db8fc1 <Antoine Pitrou> Try a more flexible way of finding Boost
d57064960 <Antoine Pitrou> ARROW-7726:   Use boost binaries on Windows GHA build

Authored-by: Antoine Pitrou <9359a4d812173b65a3a0094cd86363e79731a3c2@python.org>
Signed-off-by: Sutou Kouhei <73218711cdd5d5c30ac66da3cc4d9d9204caf34b@clear-code.com>

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