rename UNIQUE_NAME macro to UNIQUE_LOG_NAME

Summary:
This is a workaround for the build failure with mingw-w64 due to UNIQUE_NAME being defined in nb30.h https://github.com/mingw-w64/mingw-w64/blob/7f54c78e35c2056a6d972261d70e8ba8fbf1191a/mingw-w64-headers/include/nb30.h#L78
The conflict happens in a win64 build with -DBUILD_BITCOIN_CHRONIK=ON

Test Plan: @bot build-win64

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14901