Reject overflowing hash map capacities

[Old-Ding]

Summary

• preserve an overflowing power-of-two rounding result instead of silently converting it to capacity 1
• reject zero or overflowing bucket-array capacities in the shared allocation path used by initialization and growth
• allocate the bucket array using the actual rcutils_array_list_t element size

Testing

• added focused tests for rounding overflow and bucket-array size overflow
• linked a focused probe against origin/rolling: SIZE_MAX returned success with initialized=1
• linked the same probe against this change: returned RCUTILS_RET_BAD_ALLOC with initialized=0
• compiled src/hash_map.c as C11 with Zig using -Wall -Wextra -Werror
• git diff --check

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