Remove SDK C++ new/delete, duplicated objects (#2760)

* Remove Pico-SDK C++ exception-override new/delete

We support exceptions on and off, but the cxx_options file in the
SDK implemented a single override to new/delete.

Remove it so we will use GCC's build-in operator new/delete
which will be correct for either option (2 different libstdc++
versions are shipped as part of the toolchain).

* Remove duplicated SDK files

The SDK will link in the same compilation unit in the LWIP builds.
Remove them to shrink the repo size by ~28MB.

Author: earlephilhower