Move fuzzer scripts to duckdb_sqlsmith.

[hmeriann]

Move .py scripts mentioned in the duckdb's Makefile and also move any of shell scripts.

[hmeriann]

@Tmonster please see the changes

[Tmonster]

You don't need to add all of the fuzzer scripts. You can just add the ones directly related to fuzzing. I.e

- fuzzer_helper.py
- reduce_sql.py
- run_fuzzer.py
- run_sqlancer.py
- run_sqlsmith.py

[Tmonster]

And then you can see if removing these files from duckdb/duckdb will fail CI on duckdb/duckdb main

[Mytherin]

Thanks!