Hyperloglog avoid allocate more than 'server.hll_sparse_max_bytes' bytes of...
Hyperloglog avoid allocate more than 'server.hll_sparse_max_bytes' bytes of memory for sparse representation (#11438) Before this PR, we use sdsMakeRoomFor() to expand the size of hyperloglog string (sparse representation). And because sdsMakeRoomFor() uses a greedy strategy (allocate about twice what we need), the memory we allocated for the hyperloglog may be more than `server.hll_sparse_max_bytes` bytes. The memory more than` server.hll_sparse_max_bytes` will be wasted. In this pull request, tone down the greediness of the allocation growth, and also make sure it'll never request more than `server.hll_sparse_max_bytes`. This could in theory mean the size of the hyperloglog string is insufficient for the increment we need, should be ok since in this case we promote the hyperloglog to dense representation, an assertion was added to make sure. This PR also add some tests and fixes some typo and indentation issues.
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