add LockPostgreSQL and BenchmarkDistLockers

[leeym]

Add the following two

• LockPostgreSQL implements DistLocker using advisory locks in PostgreSQL
• BenchmarkDistLockers to compare the performance for distributed lockers

goarch: amd64
pkg: github.com/mennanov/limiters
cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
BenchmarkDistLockers
2024/03/16 15:44:22 Connected to 127.0.0.1:2181
2024/03/16 15:44:22 authenticated: id=72064875209293827, timeout=4000
2024/03/16 15:44:22 re-submitting `0` credentials after reconnect
BenchmarkDistLockers/LockEtcd
BenchmarkDistLockers/LockEtcd-12                     171           6576282 ns/op
BenchmarkDistLockers/LockConsul
BenchmarkDistLockers/LockConsul-12                   100          15450609 ns/op
BenchmarkDistLockers/LockZookeeper
BenchmarkDistLockers/LockZookeeper-12                265           4537545 ns/op
BenchmarkDistLockers/LockRedis
BenchmarkDistLockers/LockRedis-12                   1238            984753 ns/op
BenchmarkDistLockers/LockMemcached
BenchmarkDistLockers/LockMemcached-12                816           1608760 ns/op
BenchmarkDistLockers/LockPostgreSQL
BenchmarkDistLockers/LockPostgreSQL-12               670           1664998 ns/op

It will be easier to review in unified view and hide whitespace.

I should reopen the previous PR instead of creating a new one. Anyway, the difference is that in #38 I used session-level advisory lock. Since in the test we share the same database connection, thus the same session, between two lockers, they interfere with each other as the lock acquired by one locker can be released by the other one. In this PR I use transaction-level advisory lock, so each locker has its own transaction even if they share the same database connection.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.05%. Comparing base (c1474e1) to head (2aa986d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #39      +/-   ##
==========================================
+ Coverage   79.90%   80.05%   +0.15%     
==========================================
  Files          12       12              
  Lines        1438     1449      +11     
==========================================
+ Hits         1149     1160      +11     
  Misses        212      212              
  Partials       77       77              

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[mennanov]

Looks good!
I left just 1 small comment.

Thanks!

[mennanov]

Awesome, thanks!