lib: Document status of deprecated.nix and move it

This is all I could find after co-maintaining lib for a long time.
I've had the fortune of basically not really noticing this file,
because it has had very few interactions until the confusion in
https://github.com/NixOS/nixpkgs/pull/304277

It seems to be a state of limbo, which would be nice to resolve
(with great care), but this is not urgent, and first we should
document its status.

Changed files
+12 -1
lib
+1 -1
lib/default.nix
···
# misc
asserts = callLibs ./asserts.nix;
debug = callLibs ./debug.nix;
-
misc = callLibs ./deprecated.nix;
+
misc = callLibs ./deprecated/misc.nix;
# domain-specific
fetchers = callLibs ./fetchers.nix;
lib/deprecated.nix lib/deprecated/misc.nix
+11
lib/deprecated/README.md
···
+
+
# lib/deprecated
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Do not add any new functions to this directory.
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This directory contains the `lib.misc` sublibrary, which - as a location - is deprecated.
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Furthermore, some of the functions inside are of *dubious* utility, and should perhaps be avoided,
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while some functions *may still be needed*.
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This directory does not play a role in the deprecation process for library functions.
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They should be deprecated in place, by putting a `lib.warn` or `lib.warnIf` call around the function.