Initialize only once + tracking initializations state

[jordanflitter]

Fix #591.

This PR deletes all the calls of init_ps, initialiseSigmaMInterpTable and init_heat from the C backend. The initializations (as well as the broadcast to C) are done in the wrapper only ONCE, regardless if we run a high level function, a single field function, or something from cfuncs.py.

I moved the nested wrapper in cfuncs.py to _param_config.py. The update wrapper (whose every line was written with blood, sweat and mostly tears) contains a dynamic _InitManager instance that is passed across different levels of functions via their kwargs, allowing the functions to inspect the state of the initializations and decide whether a given initialization must be performed or not. The decorators above the functions also give an idea for what must be initialized in order for the execution to complete.

Besides the more elegant design (according to me!), this architecture reduces the runtime of run_global_evolution by 50%! (because the sigma interpolation tables are not initialized every time a single field function is called)
Moreover, it cleans some memory leak bugs (init_ps was very often not accompanied with free_ps at the end, sometimes there were even calls to init_ps without actually using the power spectrum).

Other ideas that I had but still haven't implemented them:

• Update performance.rst.
• Use the data in _InitManager to raise an error (if something was not initialized, to prevent a segfault) or a warning if the computation was complete but something was left unfreed. While this is a nice feature in theory, the architecture of the updated wrapper will make it very difficult to test these scenarios (since the whole idea is that the wrapper uses _InitManager to decide what to initialize and what not.

[codecov]

Codecov Report

❌ Patch coverage is 95.40816% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.32%. Comparing base (396b60d) to head (78c1411).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/py21cmfast/drivers/_param_config.py	92.85%	6 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #624      +/-   ##
==========================================
+ Coverage   88.16%   88.32%   +0.15%     
==========================================
  Files          32       32              
  Lines        4741     4829      +88     
  Branches      800      822      +22     
==========================================
+ Hits         4180     4265      +85     
  Misses        401      401              
- Partials      160      163       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.