UnusedIssueHandlerSuppression would be emitted for any issue handler
rather than just suppressions.

For example, this would trigger it, even if it was used:

```
<UndefinedClass errorLevel="info" />
```

This fixes up an if statement so that the issue is only emitted for
`errorLevel="suppress"`.

…eral-use

Add missing reset of context inside_general_use

…tive

Fix false positives for UnusedIssueHandlerSuppression

Fix condition on literal-string

Now the script uses its own location as a basis instead of the
current working dir.

Object property types

Allow running generate_testsuites.php from a different dir

e.g:
./vendor/bin/phpunit --filter 'Psalm\\Tests\\VariadicTest'

Call parent setUpBeforeClaass method instead of duplicating code.

Use the VersionUtils class also in AsyncTest instead of hard-coded values.

…args

Fix some more tests when running phpunit with args

Fix type of property-get with coalesce

Fix condition on lowercase-string