fixes https://github.com/llvm/llvm-project/issues/143247

RuntimeLibcallInfo needs to be accurate outside of codegen
contexts.

This consolidates node definitions into one place and enables automatic
node verification.

Part of #119709.

…on returning { i8, i128 }

Fixes https://github.com/llvm/llvm-project/issues/96432.

The nodes have one input, shift amount of 1 is implied.

This removes operands/results either in SDNode description or in ISel
code so that they match each other.

Identified with misc-include-cleaner.

Summary:
These Libcalls represent which functions are available to the backend.
If a runtime call is not available, the target sets the the name to
`nullptr`. Currently, this logic is spread around the various targets.
This patch pulls all of the locations that disable libcalls into the
intializer. This patch is effectively NFC.

The motivation behind this patch is that currently the LTO handling uses
the list of all runtime calls to determine which functions cannot be
internalized and must be extracted from static libraries. We do not want
this to happen for libcalls that are not emitted by the backend. A
follow-up patch will move out this logic so the LTO pass can know which
rtlib calls are actually used by the backend.