[flang] Do not convey captured globals through host link

Addresses and properties (bounds, length parameters) of host
variables associated in an internal procedure were all passed via
an extra tuple argument of the internal procedure.
This extra tuple is in general an overhead: it must be created and
passed, and require creating thunks when taking the address of the
internal procedure.
This patch allows not using the tuple for host global variables
(from modules, common block, or local saved variables) since they can
be instantiated from the fir.global symbol in the internal procedure
instead.
Add a fir.internal_proc attribute to mlir::FuncOp for internal procedures
so that ArrayValueCopy can still detect internal procedures even if they
do not have a tuple argument.

Differential Revision: https://reviews.llvm.org/D140288