deprecate std/threadpool; use malebolgia, weave, nim-taskpool instead (#22576)

* deprecate `std/threadpool`; use `malebolgia` instead

* Apply suggestions from code review

* Apply suggestions from code review

* change the URL of inim

(cherry picked from commit a7a0105d8c)

lib/pure/concurrency/threadpool.nim

@@ -7,6 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
+{.deprecated: "use the nimble packages `malebolgia`, `taskpools` or `weave` instead".}
+
 ## Implements Nim's `parallel & spawn statements <manual_experimental.html#parallel-amp-spawn>`_.
 ##
 ## Unstable API.

testament/important_packages.nim

@@ -80,7 +80,7 @@ pkg "gnuplot", "nim c gnuplot.nim"
 pkg "hts", "nim c -o:htss src/hts.nim"
 pkg "httpauth"
 pkg "illwill", "nimble examples"
-pkg "inim"
+pkg "inim", url = "https://github.com/nim-lang/INim"
 pkg "itertools", "nim doc src/itertools.nim"
 pkg "iterutils"
 pkg "jstin"