chore(3p): Bump channels to 2021-04-09

Fixes included:

* exposed gtest in the package set, required for protobuf
* pinned SBCL to version 2.0.8: The channel moved it to >2.1, and a
  bunch of warnings seemed to be killing our builds - we should
  investigate this later.
* removed kernel patches from //users/tazjin/frog: this machine is
  currently out of service anyways, not worth fixing while it's offline
* removed steam & lutris from frog (they're currently broken)
* removed Haskell overrides for hedgehog-classes & hgeometry-combinatorial
* use gRPC sources from upstream and inject Abseil via Nix instead
* fix for renamed grpc import in //third_party/nix
* use libfprint-tod from upstream nixpkgs in glittershark/yeren and
  delete glittershark/pkgs/fprintd entirely, since all of the patches used
  there are available and working from upstream now (and stopped working
  here after the bump)

Change-Id: Ia90e6f774f7b88bc9e60d28351b900ca43ee2695
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2901
Reviewed-by: glittershark <grfn@gws.fyi>
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Tested-by: BuildkiteCI

users/tazjin/nixos/frog/default.nix

@@ -39,9 +39,11 @@ in lib.fix(self: {
       "kernel.perf_event_paranoid" = -1;
     };
 
-    kernelPatches = [
-      depot.third_party.kernelPatches.trx40_usb_audio
-    ];
+    # Enable this again if frog is put back into use ...
+    #
+    # kernelPatches = [
+    #   depot.third_party.kernelPatches.trx40_usb_audio
+    # ];
   };
 
   hardware = {
@@ -239,7 +241,6 @@ in lib.fix(self: {
       emacs27 # mostly for emacsclient
       exa
       fd
-      ffmpeg-full
       file
       gdb
       gnupg
@@ -254,7 +255,6 @@ in lib.fix(self: {
       jq
       kubectl
       linuxPackages.perf
-      # lutris
       manpages
       miller
       msmtp
@@ -272,12 +272,10 @@ in lib.fix(self: {
       pmutils
       pwgen
       ripgrep
-      rr
       rustup
       screen
       scrot
       spotify
-      steam
       tokei
       transmission
       tree
@@ -290,6 +288,10 @@ in lib.fix(self: {
       yubico-piv-tool
       yubikey-personalization
       zoxide
+
+      # Commented out because of interim breakage:
+      # steam
+      # lutris
     ]);
 
   # ... and other nonsense.