This PR converts the TPC-H module into a proper extension. The extension can be build by setting the BUILD_TPCH_EXTENSION flag in the cmake config. When compiled in, it is included by default in the shell. The extension provides the following SQL support:

-- dbgen(sf : DOUBLE, overwrite : BOOLEAN, schema : VARCHAR, suffix : VARCHAR)
-- fills the database with the TPC-H tables, parameters are relatively self-describing
-- e.g. to load SF1:
CALL dbgen(sf=1);

-- PRAGMA tpch(query_number)
-- runs the TPC-H query number, valid numbers are in range [1, 22]
-- e.g. to run Q1:
PRAGMA tpch(1);

To enable this, the PR includes support for procedures (e.g. CALL x()) and now stores PRAGMA functions in the catalog, rather than having them be hard-coded into the engine. The interpreted benchmarks are also extended to now support loading results from a file, cleanup and init scripts, require for requiring extensions (like the sqllogictests) and benchmark templates (allowing a templated script to run another benchmark script with some string substitutions, see e.g. the TPC-H SF1 queries in benchmark/tpch/sf1/q...).