UniStore: Use epoch with microsecond resolution as RV (#92638)

* Use epoch with microsecond resolution as RV

* fix backend tests

* Add solution for when the clock goes back

* Add solution for when the clock goes back

* generate mocks

* go lint

* remove comment

* Use Greatest instead of max in msyql and postgres

* update tests

* Update pkg/storage/unified/sql/sqltemplate/dialect_sqlite.go

Co-authored-by: Diego Augusto Molina <diegoaugustomolina@gmail.com>

* cast to bigint

* add additional round trip

* increment the RV using 2 sql round trips instead of 3

* cleanup comments

* cast unix timestamp to integer

* fix postgres query

* remove old increment test data

* remove greatest

* cast unix_timestamp to signed

* Use statement_timestamp instead of clock_timestamp

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Co-authored-by: Diego Augusto Molina <diegoaugustomolina@gmail.com>

pkg/storage/unified/sql/testdata/postgres--resource_update-single path.sql

@@ -4,8 +4,8 @@ UPDATE "resource"
         "value"  = '[]',
         "action" = 'UNKNOWN'  
     WHERE 1 = 1
-        AND "group"     = ''
-        AND "resource"  = ''
-        AND "namespace" = ''
-        AND "name"      = ''
+        AND "group"     = 'gg'
+        AND "resource"  = 'rr'
+        AND "namespace" = 'nn'
+        AND "name"      = 'name'
 ;