[jmcarcell]

What does this PR do?

Explicitly default CachedTile's constructor to avoid a GCC 13.1.0 internal compiler error when initializing m_aCachedTiles in C++20 mode. The existing member initializers still initialize each tile.

Building GDAL 3.13.3 on AlmaLinux 9 with GCC 13.1.0 fails in alg/gdalgeoloc.cpp, instantiating GDALCachedPixelAccessor<double, 256, 64>:

gcore/gdalcachedpixelaccessor.h:51:9: internal compiler error: Segmentation fault
   51 |         m_aCachedTiles{};

The failure also reproduces in a standalone example containing just the nested tile type and its array. It occurs in C++20 mode, but passes in C++17. In our build, PROJ 9.9.0 exports cxx_std_20, raising GDAL's effective standard above the requested C++17.

Validation on the 3.13.3 release:

• Clean GCC 13.1.0 Debug package build: reproduced before the change; build and installation pass after it.
• Forward/inverse geolocation smoke checks pass with GDAL_GEOLOC_USE_TEMP_DATASETS=NO and YES, including the affected dataset accessor.
• The unmodified standalone example passes with GCC 14.2.0 and 16.1.0 in C++20 mode.

AI tool usage

• Codex reproduced the failure, proposed this change, ran the validation, and prepared and submitted this PR at the user's explicit request.

Environment

• AlmaLinux 9, x86_64
• GCC 13.1.0, C++20