Move all the testing creation data to a designated file #80
Description
Currently tons of tests define duplicated functions to generate the models.
As a result:
- tons of things are duplicated
- some models are complete fake and the mess up the real data flow, e.g. index Table has to guard against empty metaindex buffer which may happen only in the tests.
- Move the functions to testing.zig in the same module/folder
- Get rid of the guard in index/Table.zig .fromMem