stdenv: deprecate unused adapters

stdenv: deprecate addCoverageInstrumentation adapter

this used to be used in nixos/tests but it hasn't been used in nixpkgs
for years

stdenv: deprecate replaceMaintainersField adapter

it was added in 2009 in 01e98e49b1
by nbp
there are no uses of it in nixpkgs now

stdenv: deprecate validateLicenses adapter

it was added in 2009 in b29073af25

unfreePredicate is now handled in ./pkgs/stdenv/generic/check-meta.nix
so this is unnecessary

pkgs/stdenv/adapters.nix

@@ -149,25 +149,15 @@ rec {
   });
 
 
-  /* Return a modified stdenv that builds packages with GCC's coverage
-     instrumentation.  The coverage note files (*.gcno) are stored in
-     $out/.build, along with the source code of the package, to enable
-     programs like lcov to produce pretty-printed reports.
-  */
+  # remove after 22.05 and before 22.11
   addCoverageInstrumentation = stdenv:
+    builtins.trace "'addCoverageInstrumentation' adapter is deprecated and will be removed before 22.11"
     overrideInStdenv stdenv [ pkgs.enableGCOVInstrumentation pkgs.keepBuildTree ];
 
 
-  /* Replace the meta.maintainers field of a derivation.  This is useful
-     when you want to fork to update some packages without disturbing other
-     developers.
-
-     e.g.:  in all-packages.nix:
-
-     # remove all maintainers.
-     defaultStdenv = replaceMaintainersField allStdenvs.stdenv pkgs [];
-  */
+  # remove after 22.05 and before 22.11
   replaceMaintainersField = stdenv: pkgs: maintainers:
+    builtins.trace "'replaceMaintainersField' adapter is deprecated and will be removed before 22.11"
     stdenv.override (old: {
       mkDerivationFromStdenv = overrideMkDerivationResult (pkg:
         lib.recursiveUpdate pkg { meta.maintainers = maintainers; });
@@ -193,22 +183,9 @@ rec {
     });
 
 
-  /* Abort if the license predicate is not verified for a derivation
-     declared with mkDerivation.
-
-     One possible predicate to avoid all non-free packages can be achieved
-     with the following function:
-
-     isFree = license: with builtins;
-       if license == null then true
-       else if isList license then lib.all isFree license
-       else license != "non-free" && license != "unfree";
-
-     This adapter can be defined on the defaultStdenv definition.  You can
-     use it by patching the all-packages.nix file or by using the override
-     feature of ~/.config/nixpkgs/config.nix .
-  */
+  # remove after 22.05 and before 22.11
   validateLicenses = licensePred: stdenv:
+    builtins.trace "'validateLicenses' adapter is deprecated and will be removed before 22.11"
     stdenv.override (old: {
       mkDerivationFromStdenv = overrideMkDerivationResult (pkg:
         let