Move os_memdup into src/utils/allocs

[aloisklink]

Move os_memdup from src/radius/common.h into src/utils/allocs.h.

This function should be with all the other memory allocation functions, so that we can give it a C23 [[nodiscard]] attribute (or GCC/Clang equivalent attribute, since we don't yet support C23).

This PR also documents that the implementation of os_memdup was adapted from commit
dbdda35 in hostapd.

---

Kind of confusingly, there's actually two versions of the function in PR #380.

os_memdup in src/radius/common.h:

edgesec/src/radius/common.h

Lines 179 to 189 in 666a609

	/**
	* @brief Allocate duplicate of passed memory chunk
	*
	* This function allocates a memory block like os_malloc() would, and
	* copies the given source buffer into it.
	*
	* @param src Source buffer to duplicate
	* @param len Length of source buffer
	* @return void* %NULL if allocation failed, copy of src buffer otherwise
	*/
	static inline void *os_memdup(const void *src, size_t len) {

sys_memdup in src/utils/allocs.h (this one was added in commit 24a8d46):

edgesec/src/utils/allocs.h

Lines 32 to 42 in 666a609

	/**
	* os_memdup - Allocate duplicate of passed memory chunk
	*
	* This function allocates a memory block like os_malloc() would, and
	* copies the given source buffer into it.
	*
	* @param src Source buffer to duplicate
	* @param len Length of source buffer
	* @return void* %NULL if allocation failed, copy of src buffer otherwise
	*/
	void *sys_memdup(const void *src, size_t len);

I've decided to stick my version of this function into src/utils/allocs.h, since @mereacre commited it later in 24a8d46.

Plus, having it in allocs makes more sense, since it also makes it easier for us to add a [[nodiscard]] attribute to the function, so that the compiler throws an error if we don't do anything with the return value of the function.

[codecov]

Codecov Report

Merging #429 (918301c) into main (ba237fd) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main     #429   +/-   ##
=======================================
  Coverage   53.09%   53.09%           
=======================================
  Files         144      144           
  Lines       19880    19880           
=======================================
  Hits        10555    10555           
  Misses       9325     9325           

Impacted Files	Coverage Δ
src/radius/common.h	42.59% <ø> (+3.60%)	⬆️
src/utils/allocs.h	45.45% <0.00%> (-37.88%)	⬇️

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