GH-46111: [C++][CI] Fix boost 1.88 on MinGW (#46113)

### Rationale for this change

Boost has remove their `include/boost/process/v1.hpp`

### What changes are included in this PR?

Instead of using their old include file (which was a wrapper for the different includes) add the individual includes.

### Are these changes tested?

Via CI.

### Are there any user-facing changes?

No
* GitHub Issue: #46111

Authored-by: Raúl Cumplido <[email protected]>
Signed-off-by: Raúl Cumplido <[email protected]>

Author: raulcd

cpp/src/arrow/testing/process.cc

@@ -57,7 +57,24 @@
 #      define BOOST_USE_WINDOWS_H = 1
 #    endif
 #    ifdef BOOST_PROCESS_HAVE_V1
-#      include <boost/process/v1.hpp>
+#      include <boost/process/v1/args.hpp>
+#      include <boost/process/v1/async.hpp>
+#      include <boost/process/v1/async_system.hpp>
+#      include <boost/process/v1/child.hpp>
+#      include <boost/process/v1/cmd.hpp>
+#      include <boost/process/v1/env.hpp>
+#      include <boost/process/v1/environment.hpp>
+#      include <boost/process/v1/error.hpp>
+#      include <boost/process/v1/exe.hpp>
+#      include <boost/process/v1/group.hpp>
+#      include <boost/process/v1/handles.hpp>
+#      include <boost/process/v1/io.hpp>
+#      include <boost/process/v1/pipe.hpp>
+#      include <boost/process/v1/search_path.hpp>
+#      include <boost/process/v1/shell.hpp>
+#      include <boost/process/v1/spawn.hpp>
+#      include <boost/process/v1/start_dir.hpp>
+#      include <boost/process/v1/system.hpp>
 #    else
 #      include <boost/process.hpp>
 #    endif