Following RFC at
https://discourse.llvm.org/t/rfc-ffp-contract-default-value/66301
This adds the `fastmath<contract>` attribute to `fir.call` and some
floating point arithmetic operations (hence the many test changes).
Instead of testing for this specific attribute, I am using a regular
expression to match any attributes.
Lowering was truncating 128 bits integer to 64 bits. This
patch makes use of APInt to lower 128 bits integer correctly.
```
program bug
print *, 170141183460469231731687303715884105727_16
end
! Before patch: 18446744073709551615
! With patch: 170141183460469231731687303715884105727
```
Reviewed By: vdonaldson
Differential Revision: https://reviews.llvm.org/D133206