[flang][acc] Improve acc lowering around fir.box and arrays (#125600)

The current implementation of OpenACC lowering includes explicit
expansion of following cases:
- Creation of `acc.bounds` operations for all arrays, including those
whose dimensions are captured in the type (eg `!fir.array<100xf32>`)
- Expansion of box types by only putting the box's address in the data
clause. The address was extracted with a `fir.box_addr` operation and
the bounds were filled with `fir.box_dims` operation.

However, with the creation of the new type interface `MappableType`, the
idea is that specific type-based semantics can now be used. This also
really simplifies representation in the IR. Consider the following
example:
```
subroutine sub(arr)
  real :: arr(:)
  !$acc enter data copyin(arr)
end subroutine
```

Before the current PR, the relevant acc dialect IR looked like:
```
func.func @_QPsub(%arg0: !fir.box<!fir.array<?xf32>> {fir.bindc_name =
"arr"}) {
  ...
  %1:2 = hlfir.declare %arg0 dummy_scope %0 {uniq_name = "_QFsubEarr"} :
(!fir.box<!fir.array<?xf32>>, !fir.dscope) ->
(!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
  %c1 = arith.constant 1 : index
  %c0 = arith.constant 0 : index
  %2:3 = fir.box_dims %1#0, %c0 : (!fir.box<!fir.array<?xf32>>, index)
-> (index, index, index)
  %c0_0 = arith.constant 0 : index
  %3 = arith.subi %2#1, %c1 : index
  %4 = acc.bounds lowerbound(%c0_0 : index) upperbound(%3 : index)
extent(%2#1 : index) stride(%2#2 : index) startIdx(%c1 : index)
{strideInBytes = true}
  %5 = fir.box_addr %1#0 : (!fir.box<!fir.array<?xf32>>) ->
!fir.ref<!fir.array<?xf32>>
  %6 = acc.copyin varPtr(%5 : !fir.ref<!fir.array<?xf32>>) bounds(%4) ->
!fir.ref<!fir.array<?xf32>> {name = "arr", structured = false}
  acc.enter_data dataOperands(%6 : !fir.ref<!fir.array<?xf32>>)
```

After the current change, it looks like:
```
func.func @_QPsub(%arg0: !fir.box<!fir.array<?xf32>> {fir.bindc_name =
"arr"}) {
  ...
  %1:2 = hlfir.declare %arg0 dummy_scope %0 {uniq_name = "_QFsubEarr"} :
(!fir.box<!fir.array<?xf32>>, !fir.dscope) ->
(!fir.box<!fir.array<?xf32>>, !fir.box<!fir.array<?xf32>>)
  %2 = acc.copyin var(%1#0 : !fir.box<!fir.array<?xf32>>) ->
!fir.box<!fir.array<?xf32>> {name = "arr", structured = false}
  acc.enter_data dataOperands(%2 : !fir.box<!fir.array<?xf32>>)
```

Restoring the old behavior can be done with following command line
options:
`--openacc-unwrap-fir-box=true --openacc-generate-default-bounds=true`