Toolchain update for Windows builds of DuckDB

Hi R client maintainers! We are changing the toolchain that is used on DuckDB CI to produce Windows binaries, details: - duckdb/duckdb#21371 - duckdb/extension-ci-tools#343 Currently the following MinGW build is used: ``` https://github.com/niXman/mingw-builds-binaries/releases/download/14.2.0-rt_v12-rev0/x86_64-14.2.0-release-posix-seh-ucrt-rt_v12-rev0.7z ``` The the GCC version `14.2` was chosen to stay closer to release Linux builds. We can change the toolchain if necessary, please let us know if it is better to use different kind/version of MinGW binaries. Besides R these binaries are also used by Golang client.