Use _Alignof to query alignments in the struct module

# Feature or enhancement

### Proposal:

The struct module uses pre-C11 hacks to determine alignment for types:
https://github.com/python/cpython/blob/580888927c8eafbf3d4c6be9144684117f0a96ca/Modules/_struct.c#L79-L106

Now we can use `_Alignof` operator, as C11-compatible compiler is a build requireent.

### Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

### Links to previous discussion of this feature:

_No response_


### Linked PRs
* gh-132872

	/* Define various structs to figure out the alignments of types */


	typedef struct { char c; short x; } st_short;
	typedef struct { char c; int x; } st_int;
	typedef struct { char c; long x; } st_long;
	typedef struct { char c; float x; } st_float;
	typedef struct { char c; double x; } st_double;
	#ifdef Py_HAVE_C_COMPLEX
	typedef struct { char c; float complex x; } st_float_complex;
	typedef struct { char c; double complex x; } st_double_complex;
	#endif
	typedef struct { char c; void *x; } st_void_p;
	typedef struct { char c; size_t x; } st_size_t;
	typedef struct { char c; _Bool x; } st_bool;

	#define SHORT_ALIGN (sizeof(st_short) - sizeof(short))
	#define INT_ALIGN (sizeof(st_int) - sizeof(int))
	#define LONG_ALIGN (sizeof(st_long) - sizeof(long))
	#define FLOAT_ALIGN (sizeof(st_float) - sizeof(float))
	#define DOUBLE_ALIGN (sizeof(st_double) - sizeof(double))
	#ifdef Py_HAVE_C_COMPLEX
	# define FLOAT_COMPLEX_ALIGN (sizeof(st_float_complex) - sizeof(float complex))
	# define DOUBLE_COMPLEX_ALIGN (sizeof(st_double_complex) - sizeof(double complex))
	#endif
	#define VOID_P_ALIGN (sizeof(st_void_p) - sizeof(void *))
	#define SIZE_T_ALIGN (sizeof(st_size_t) - sizeof(size_t))
	#define BOOL_ALIGN (sizeof(st_bool) - sizeof(_Bool))

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Use _Alignof to query alignments in the struct module #132868

Feature or enhancement

Proposal:

Has this already been discussed elsewhere?

Links to previous discussion of this feature:

Linked PRs

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Uh oh!

Use _Alignof to query alignments in the struct module #132868

Description

Feature or enhancement

Proposal:

Has this already been discussed elsewhere?

Links to previous discussion of this feature:

Linked PRs

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

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