💥 Replace exec-path-from-shell w/ 'bin/doom env'

IMPORTANT: This is a breaking update for Mac users, as your shell
environment will no longer be inherited correctly (with the removal of
exec-path-from-shell). The quick fix is: 'bin/doom env refresh'. Also,
the set-env! autodef now does nothing (and is deprecated), be sure to
remove calls to it in your config.

Smaller changes:
+ This update also adds --no-* switches to doom quickstart
+ Includes general improvements to the documentation of several bin/doom
  commands.
+ Moves doom/reload* commands to core/autoload/config.el
+ doom/reload-project has been removed (it didn't actually do anything)

The breaking change:
This update adds an "envvar file" to Doom Emacs. This file is generated
by `doom env refresh`, populated with variables scraped from your shell
environment (from both non-interactive and interactive sessions). This
file is then (inexpensively) loaded at startup, if it exists.

+ The file is manually generated with `doom env refresh`.
+ It can be regenerated automatically whenever `doom refresh` is run by
  running `doom env enable` (`doom env clear` will reverse this and
  delete the env file).
+ `doom quickstart` will ask if you want to auto-generate this envvar
  file. You won't need it if you're confident Emacs will always be
  started from the correct environment, however.
+ Your env file can be reloaded from a running Emacs session with `M-x
  doom/reload-env`. Note: this won't work if the Emacs session you're
  running it in doesn't have a correct SHELL set. i.e. don't use this to
  create your first env file!

The idea isn't mine -- it's borrowed from Spacemacs -- and was
introduced to me in #1053 by @yurimx. I was impressed with it. Prior to
this, I was unhappy with exec-path-from-shell (no hate to the dev, I
understand its necessity), and 'doom patch-macos' wasn't ideal for mac
users (needed to be reapplied every time you update Emacs). What's more,
many users (even Linux users) had to install exec-path-from-shell
anyway.

This solution suffers from none of their shortcomings. More reliable
than patch-macos, more performant and complete than
exec-path-from-shell, and easily handled by bin/doom.

core/core-cli.el

@@ -107,7 +107,8 @@ best to run Doom out of ~/.emacs.d and ~/.doom.d.")
 (dispatcher! (doctor doc) :noop
   "Checks for issues with your environment & Doom config.
 
-Also checks for missing dependencies for any enabled modules.")
+Use the doctor to diagnose common problems or list missing dependencies in
+enabled modules.")
 
 (dispatcher! (help h) :noop
   "Look up additional information about a command.")
@@ -119,6 +120,7 @@ Also checks for missing dependencies for any enabled modules.")
 (load! "cli/autoloads")
 (load! "cli/byte-compile")
 (load! "cli/debug")
+(load! "cli/env")
 (load! "cli/packages")
 (load! "cli/patch-macos")
 (load! "cli/quickstart")
@@ -131,6 +133,8 @@ Also checks for missing dependencies for any enabled modules.")
   "Ensure Doom is in a working state by checking autoloads and packages, and
 recompiling any changed compiled files. This is the shotgun solution to most
 problems with doom."
+  (when (getenv "DOOMENV")
+    (doom-reload-env-file 'force))
   (doom-reload-doom-autoloads force-p)
   (unwind-protect
       (progn
@@ -142,7 +146,7 @@ problems with doom."
     (doom-byte-compile nil 'recompile)))
 
 (dispatcher! (refresh re) (doom-refresh 'force)
-  "Refresh Doom. Same as autoremove+install+autoloads.
+  "Refresh Doom.
 
 This is the equivalent of running autoremove, install, autoloads, then
 recompile. Run this whenever you:
@@ -150,7 +154,11 @@ recompile. Run this whenever you:
   1. Modify your `doom!' block,
   2. Add or remove `package!' blocks to your config,
   3. Add or remove autoloaded functions in module autoloaded files.
-  4. Update Doom outside of Doom (e.g. with git)")
+  4. Update Doom outside of Doom (e.g. with git)
+
+It will ensure that unneeded packages are removed, all needed packages are
+installed, autoloads files are up-to-date and no byte-compiled files have gone
+stale.")
 
 (provide 'core-cli)
 ;;; core-cli.el ends here