Cannot create unions with bitfields when creating a type with C source

Version and Platform (required):

• Binary Ninja Version: 5.2.8464-dev (ea2f9317)
• Edition: Commercial
• OS: macOS
• OS Version: 15.5
• CPU Architecture: M1

Bug Description:
Unions do not allow for bitfields when creating them via C source.

Steps To Reproduce:

1. Load a binary view.
2. Open "Create Types from C source"
3. Create a type using the following source:

union Test
{
    uint8_t foo : 1;
    uint16_t bar : 2;
};

4. Observe the created type will look like this where the fields are not bitfields:

union Test
{
    uint8_t foo;
    uint16_t bar;
};

Additional Information:
Creating the same type using the python API works as expected:

builder = binaryninja.TypeBuilder.structure()
builder.type = StructureVariant.UnionStructureType
builder.add_member_at_offset("foo", Type.int(1), offset=0, bit_position=0, bit_width=1, overwrite_existing=False)
builder.add_member_at_offset("bar", Type.int(2), offset=0, bit_position=0, bit_width=2, overwrite_existing=False)
bv.define_user_type("Test", builder.immutable_copy())

Results in:

union Test
{
    char foo : 1;
    int16_t bar : 2;
};