Optimization: sdsRemoveFreeSpace to avoid realloc on noop (#11766)
In #7875 (Redis 6.2), we changed the sds alloc to be the usable allocation size in order to: > reduce the need for realloc calls by making the sds implicitly take over the internal fragmentation This change was done most sds functions, excluding `sdsRemoveFreeSpace` and `sdsResize`, the reason is that in some places (e.g. clientsCronResizeQueryBuffer) we call sdsRemoveFreeSpace when we see excessive free space and want to trim it. so if we don't trim it exactly to size, the caller may still see excessive free space and call it again and again. However, this resulted in some excessive calls to realloc, even when there's no need and it's gonna be a no-op (e.g. when reducing 15 bytes allocation to 13). It turns out that a call for realloc with jemalloc can be expensive even if it ends up doing nothing, so this PR adds a check using `je_nallocx`, which is cheap to avoid the call for realloc. in addition to that this PR unifies sdsResize a...
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