[CIR][NFC] Use arrangeFunctionDeclaration to build function types (#139787)
This change replaces the simplified call that we were previously using
to convert the function type provided by a global declaration to the CIR
function type. We now go through 'arrangeGlobalDeclaration' which builds
the function type in a more complicated manner. This change has no
observable differences for the currently upstreamed CIR support, but it
is necessary to prepare for C++ member function calls, which require the
extra handling.