pgsql: Introduce hash_search_with_hash_value() function

Introduce hash_search_with_hash_value() function

This new function iterates hash entries with given hash values.  This function
is designed to avoid full sequential hash search in the syscache invalidation
callbacks.

Discussion: https://postgr.es/m/5812a6e5-68ae-4d84-9d85-b443176966a1%40sigaev.ru
Author: Teodor Sigaev
Reviewed-by: Aleksander Alekseev, Tom Lane, Michael Paquier, Roman Zharkov
Reviewed-by: Andrei Lepikhov

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d0f020037e19c33c74d683eb7e0c7cc5725294b4

Modified Files
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src/backend/utils/hash/dynahash.c | 38 ++++++++++++++++++++++++++++++++++++++
src/include/utils/hsearch.h       |  5 +++++
2 files changed, 43 insertions(+)