Cleaner local caching of Tex/Text data, and partially cleaned up configuration (#2259)

* Remove print("Reloading...")

* Change where exception mode is set, to be quieter

* Add default fallback monitor for when no monitors are detected

* Have StringMobject work with svg strings rather than necessarily writing to file

Change SVGMobject to allow taking in a string of svg code as an input

* Add caching functionality, and have Tex and Text both use it for saved svg strings

* Clean up tex_file_writing

* Get rid of get_tex_dir and get_text_dir

* Allow for a configurable cache location

* Make caching on disk a decorator, and update implementations for Tex and Text mobjects

* Remove stray prints

* Clean up how configuration is handled

In principle, all we need here is that manim looks to the default_config.yaml file, and updates it based on any local configuration files, whether in the current working directory or as specified by a CLI argument.

* Make the default size for hash_string an option

* Remove utils/customization.py

* Remove stray prints

* Consolidate camera configuration

This is still not optimal, but at least makes clearer the way that importing from constants.py kicks off some of the configuration code.

* Factor out configuration to be passed into a scene vs. that used to run a scene

* Use newer extract_scene.main interface

* Add clarifying message to note what exactly is being reloaded

* Minor clean up

* Minor clean up

* If it's worth caching to disk, then might as well do so in memory too during development

* No longer any need for custom hash_seeds in Tex and Text

* Remove display_during_execution

* Get rid of (no longer used) mobject_data directory reference

* Remove get_downloads_dir reference from register_font

* Update where downloads go

* Easier use of subdirectories in configuration

* Add new pip requirements