nixos-containers: add TimeoutStartSec option

Default is now 1m instead of global default of 15sec. It is also
configurable.

Fixes issue where start of many containers (40+) fail
https://github.com/NixOS/nixpkgs/issues/65001

nixos/modules/virtualisation/containers.nix

@@ -256,6 +256,10 @@ let
     RestartForceExitStatus = "133";
     SuccessExitStatus = "133";
 
+    # Some containers take long to start
+    # especially when you automatically start many at once
+    TimeoutStartSec = cfg.timeoutStartSec;
+
     Restart = "on-failure";
 
     Slice = "machine.slice";
@@ -423,6 +427,7 @@ let
       extraVeths = {};
       additionalCapabilities = [];
       ephemeral = false;
+      timeoutStartSec = "15s";
       allowedDevices = [];
       hostAddress = null;
       hostAddress6 = null;
@@ -595,6 +600,18 @@ in
               '';
             };
 
+		    timeoutStartSec = mkOption {
+		      type = types.str;
+		      default = "1min";
+		      description = ''
+		        Time for the container to start. In case of a timeout,
+		        the container processes get killed.
+		        See <citerefentry><refentrytitle>systemd.time</refentrytitle>
+		        <manvolnum>7</manvolnum></citerefentry>
+		        for more information about the format.
+		       '';
+		    };
+
             bindMounts = mkOption {
               type = with types; loaOf (submodule bindMountOpts);
               default = {};