move Rule* tests into separate testsuite

[staabm]

we should move all RuleTests* within https://github.com/staabm/phpstan-dba/tree/main/tests/default (and their corresponding Fixture/data/config) into a new main/tests/rules/ test-suite.

this would help separating the different phpstan-dba feature and therefore ease finishing #261

[staabm]

on it