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

---------

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

pkg/storage/unified/sql/testdata/mysql--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'
 ;