Multi-format test suite

[stephenberry]

In order to efficiently add and maintain lots of formats in Glaze, we need a suite of tests that will write from C++ memory, decode, and then check for roundtrip matching. These kinds of tests can handle any format. They do not handle all test cases, such as outside sources of the format, but they can test large amounts of the code while being format agnostic. You can then have CMake generate the format to generate a variety of tests based on the supported formats.

• This only applies to round-trippable formats.

[stephenberry]

Initial support has been added in #1380