treewide: automatically md-convert option descriptions

the conversion procedure is simple:

 - find all things that look like options, ie calls to either `mkOption`
   or `lib.mkOption` that take an attrset. remember the attrset as the
   option
 - for all options, find a `description` attribute who's value is not a
   call to `mdDoc` or `lib.mdDoc`
 - textually convert the entire value of the attribute to MD with a few
   simple regexes (the set from mdize-module.sh)
 - if the change produced a change in the manual output, discard
 - if the change kept the manual unchanged, add some text to the
   description to make sure we've actually found an option. if the
   manual changes this time, keep the converted description

this procedure converts 80% of nixos options to markdown. around 2000
options remain to be inspected, but most of those fail the "does not
change the manual output check": currently the MD conversion process
does not faithfully convert docbook tags like <code> and <package>, so
any option using such tags will not be converted at all.

nixos/modules/services/hardware/undervolt.nix

@@ -42,7 +42,7 @@ in
     verbose = mkOption {
       type = types.bool;
       default = false;
-      description = ''
+      description = lib.mdDoc ''
         Whether to enable verbose logging.
       '';
     };
@@ -51,7 +51,7 @@ in
       type = types.package;
       default = pkgs.undervolt;
       defaultText = literalExpression "pkgs.undervolt";
-      description = ''
+      description = lib.mdDoc ''
         undervolt derivation to use.
       '';
     };
@@ -59,7 +59,7 @@ in
     coreOffset = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The amount of voltage in mV to offset the CPU cores by.
       '';
     };
@@ -67,7 +67,7 @@ in
     gpuOffset = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The amount of voltage in mV to offset the GPU by.
       '';
     };
@@ -75,7 +75,7 @@ in
     uncoreOffset = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The amount of voltage in mV to offset uncore by.
       '';
     };
@@ -83,7 +83,7 @@ in
     analogioOffset = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The amount of voltage in mV to offset analogio by.
       '';
     };
@@ -91,7 +91,7 @@ in
     temp = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The temperature target in Celsius degrees.
       '';
     };
@@ -99,7 +99,7 @@ in
     tempAc = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The temperature target on AC power in Celsius degrees.
       '';
     };
@@ -107,7 +107,7 @@ in
     tempBat = mkOption {
       type = types.nullOr types.int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The temperature target on battery power in Celsius degrees.
       '';
     };
@@ -115,7 +115,7 @@ in
     p1.limit = mkOption {
       type = with types; nullOr int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The P1 Power Limit in Watts.
         Both limit and window must be set.
       '';
@@ -123,7 +123,7 @@ in
     p1.window = mkOption {
       type = with types; nullOr (oneOf [ float int ]);
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The P1 Time Window in seconds.
         Both limit and window must be set.
       '';
@@ -132,7 +132,7 @@ in
     p2.limit = mkOption {
       type = with types; nullOr int;
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The P2 Power Limit in Watts.
         Both limit and window must be set.
       '';
@@ -140,7 +140,7 @@ in
     p2.window = mkOption {
       type = with types; nullOr (oneOf [ float int ]);
       default = null;
-      description = ''
+      description = lib.mdDoc ''
         The P2 Time Window in seconds.
         Both limit and window must be set.
       '';
@@ -149,7 +149,7 @@ in
     useTimer = mkOption {
       type = types.bool;
       default = false;
-      description = ''
+      description = lib.mdDoc ''
         Whether to set a timer that applies the undervolt settings every 30s.
         This will cause spam in the journal but might be required for some
         hardware under specific conditions.