[CIR] Add ComputeVolatileBitfields Implementation (#151252)

This PR adds the implementation of the `ComputeVolatileBitfields`
function for the AAPCS ABI, following the rules described in [AAPCS64
§8.1.8.5 Volatile
Bit-fields](https://github.com/ARM-software/abi-aa/blob/f52e1ad3f81254497a83578dc102f6aac89e52d0/aapcs64/aapcs64.rst#8185volatile-bit-fields----preserving-number-and-width-of-container-accesses).
When accessing a volatile bit-field either reading or writing the
compiler must perform a load or store using the access size that matches
the width of the declared type (i.e., the type of the container), rather
than the packed bit-field size.
For example, if a field is declared as `int`, it must read or write 32
bits, even if the bit-field is only 3 bits wide.
The `ComputeVolatileBitfields` function calculates the correct values
and offsets necessary for proper lowering of volatile bitfields.
Support for emitting calls to `get_bitfield` and `set_bitfield` with the
correct access size for volatile bitfields will be implemented in a
future PR.

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