pgsql: Use pg_bitutils for HyperLogLog.

Use pg_bitutils for HyperLogLog.

Using pg_leftmost_one_post32() yields substantial performance benefits.

Backpatching to version 13 because HLL is used for HashAgg
improvements in 9878b643, which was also backpatched to 13.

Reviewed-by: Peter Geoghegan
Discussion: https://postgr.es/m/CAH2-WzkGvDKVDo+0YvfvZ+1CE=iCi88DCOGFF3i1hTGGaxcKPw@mail.gmail.com
Backpatch-through: 13

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/fd734f387d8780d9989d750942d026167de8cf3c

Modified Files
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src/backend/lib/hyperloglog.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)