Follow on from WT-9287.

gdb scripts will have helper functions such as list_sessions() which can be used by multiple scripts. We should create a folder structure to contain all these common functions and types that can be imported by the gdb scripts.

I hit an issue with namespacing on my first attempt (see this comment) where all importsm must be qualified from the root tools/gdb directory. This will also need fixing.

Scope of this ticket:

• Create the new common scripts dir for python scripts like tools/gdb/hazard_pointers.py to import from. This will contain functions like the existing find_sessions() and type definitions like SESSION_IMPL_PTR = gdb.lookup_type("WT_SESSION_IMPL").pointer().

• Think about proper naming/ordering of our python scripts. Existing scripts like hazard_pointer.py and dump_insert_list.py can be renamed.

• Think about the naming hierarchy of the gdb functions. We have an existing function dump_hazard_pointers. Would it make more sense to instead call it hazard_pointers_dump_all for easier tab completion?