text: Title: Refactoring: soft split xonsh into components
  Body: ### Motivation
  
  Our code and docs are mostly like a list:
  * We have news with Added/Changed/Deprecated sections.
  * We have release notes also as Added/Changed/Deprecated sections.
  * We have plain list of modules in `./xonsh/*.py` and in `./xonsh/tests/`
  * We have list of labels in issue tracker
  * The names of enviroment variables haven't name of component that will be changed.
  
  This approach looks a bit legacy today because it makes understanding harder:
  * What module for what component?
  * What component of xonsh was changed? What was changed?
  * What component address this test or this issue?
  * How to filter certain components for tracing with [xunter](https://github.com/anki-code/xunter)?
  
  To make xonsh structure more clean we need to soft grouping xonsh components/modules. "Soft" means just moving existing code into the submodules without global refactoring of everything. 
  
  I see three layers for now:
  
  - top level `xonsh/<component>`
  - libraries and component implementation in `xonsh/<component>/*`
  - common libs `./xonsh/lib`
  
  And here is what I see as first steps:
  
  1. Xonsh modules structure
  
      - [x] Move `ptk_shell`, `dumbshell`, `readline`, `ansi_color`, `color_tools` to `./xonsh/shells/`.
      - [x] Move `lexer`, `tokenize`, `ast`, etc to `./xonsh/parsers/`
      - [x] Create `xonsh.api`
      - [x] Move libraries to `xonsh.lib`
      - [ ] Move `xonfig`, `webconfig`, `wizard`, `xonitrb`, `tracer`, to `./xonsh/built_ins/`. Wait for #5543
  
  2. News and release notes
  
      - [ ] Create new template with top level components. Instead of "Added/Changed" we need to have Main, Prompt, Subprocess, Aliases, History, etc sections. This structure the changes looks more clear. Real life example of this is [release notes in xxh project](https://github.com/xxh/xxh/releases/tag/0.4.4). Probably one day we can use top level module name as the name of the section to group release notes automatically.
  
  3. Environ
  
      - Align https://xon.sh/envvars.html sections with the list of components.
              * First step: #5501
              * Next: #5149
  
  
  ## For community
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