ARROW-7597: [C++] More compact CMake configuration summary
ARROW-7597: [C++] More compact CMake configuration summary

This moves the option values right next to the option name and makes it so they can be easily copy-and-pasted for use with `-D` in build scripts. Blank lines between options are also removed

Closes #6193 from wesm/cpp-compact-build-summary and squashes the following commits:

ffd2c1895 <Wes McKinney> Incorporate feedback
3131d2185 <Wes McKinney> More compact build summary

Authored-by: Wes McKinney <3be70eed0275ec2606f002bff3514252e145d204@apache.org>
Signed-off-by: Wes McKinney <3be70eed0275ec2606f002bff3514252e145d204@apache.org>

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