NFC: Use #ifndef in various .td files instead of #ifdef and #else

Upstream LLVM gained support for #ifndef with https://reviews.llvm.org/D61888

This is changed mechanically via the following command:

find . -name "*.td" -exec sed -i -e ':a' -e 'N' -e '$!ba' -e 's/#ifdef \([A-Z_]*\)\n#else/#ifndef \1/g' {} \;

PiperOrigin-RevId: 277789427