Feature: Split off GDAL scanner into separate extension

[Maxxen]

While GDAL is an amazingly useful library the maintenance burden of getting it to statically link and compile on all platforms is kind of wearing me out. I'm also not sure if having it statically linked is 100% desirable, as you may want to have some specific driver available or use the version available on your system.

I also think GDAL is currently the main blocker for WASM. Since we can't use openssl or libcurl (I think?) we would have to add a special case for it in the build system anyway.

Once we have native support for the common geospatial formats, (see #12 #13 #14) we should look into splitting this part of the extension into a separate extension. The only common dependencies these two extensions would have then is the WKB_BLOB type, but since its just an alias we could very easily check the catalog if its already defined to allow for nice interoperability between the extensions.

[Maxxen]

This is probably not going to happen in a while, so closing for now.