LLVM IR Dialect conversion: use builder arguments instead of named attributes

The first version of TableGen-defined LLVM IR Dialect did not include the
mandatory or optional attributes of the operations due to the missing support
for some of the relevant attribute types.  This support has been recently
introduced, along with named attributes as arguments in the TableGen operation
definitions.  With these changes, LLVM IR Dialect operations now have factory
functions accepting (unnamed) attributes and attaching their canonical names.
Use these factories instead of manually constructing named attributes in the
dialect convreter to avoid hardcoded attribute names in unexpected places.

PiperOrigin-RevId: 237237769