Add CI for pull requests

[Here is a workflow](https://github.com/duckdb/duckdb_sqlsmith/blob/main/.github/workflows/test-fuzzer-ci-still-works.yml) that should run whenever a pull request is created. For some reason it doesn't anymore. Might be to do with the workflow dispatch parameter. It should also be similar to the workflow file in the `duckdb-fuzzer-ci` repository. Maybe we could also have a CI job that checks that the two files always stay the same? Theoretically I think you can just rip the GitHub actions file form the duckdb-fuzzer-ci