Generate symbols.map files using clang-extract-api

[mattkae]

Why

• This would be a revival of this pr, although a little different: Auto generate symbols map #2517
• We would like to expose all internal headers in Mir and mark them as internal in the .so file. While we could write these all out by hand, it is bound to be tedious and very error prone. We could lean on our tooling to generate these files

How

• We could use clang-extract-api or clang-query to generate info for all of our header files
• We could then write a python script that gets this info and generates a symbols.map file based on it
• The versioning info would have to come from tags in comments (maybe?)

[mattkae]

Completed!

[wmww]

yay!