tests.writers: use dashes instead of underscores in drv names

This is more in line with standard derivation name policy in nixpkgs.

pkgs/build-support/writers/test.nix

@@ -13,11 +13,11 @@ with writers;
 let
 
   bin = {
-    bash = writeBashBin "test_writers_bash_bin" ''
+    bash = writeBashBin "test-writers-bash-bin" ''
      if [[ "test" == "test" ]]; then echo "success"; fi
     '';
 
-    c = writeCBin "test_writers_c" { libraries = [ ]; } ''
+    c = writeCBin "test-writers-c" { libraries = [ ]; } ''
       #include <stdio.h>
       int main() {
         printf("success\n");
@@ -25,17 +25,17 @@ let
       }
     '';
 
-    dash = writeDashBin "test_writers_dash_bin" ''
+    dash = writeDashBin "test-writers-dash-bin" ''
      test '~' = '~' && echo 'success'
     '';
 
-    rust = writeRustBin "test_writers_rust_bin" {} ''
+    rust = writeRustBin "test-writers-rust-bin" {} ''
       fn main(){
         println!("success")
       }
     '';
 
-    haskell = writeHaskellBin "test_writers_haskell_bin" { libraries = [ haskellPackages.acme-default ]; } ''
+    haskell = writeHaskellBin "test-writers-haskell-bin" { libraries = [ haskellPackages.acme-default ]; } ''
       import Data.Default
 
       int :: Int
@@ -47,7 +47,7 @@ let
         _ -> print "fail"
     '';
 
-    js = writeJSBin "test_writers_js_bin" { libraries = [ nodePackages.semver ]; } ''
+    js = writeJSBin "test-writers-js-bin" { libraries = [ nodePackages.semver ]; } ''
       var semver = require('semver');
 
       if (semver.valid('1.2.3')) {
@@ -57,12 +57,12 @@ let
       }
     '';
 
-    perl = writePerlBin "test_writers_perl_bin" { libraries = [ perlPackages.boolean ]; } ''
+    perl = writePerlBin "test-writers-perl-bin" { libraries = [ perlPackages.boolean ]; } ''
       use boolean;
       print "success\n" if true;
     '';
 
-    python2 = writePython2Bin "test_writers_python2_bin" { libraries = [ python2Packages.enum ]; } ''
+    python2 = writePython2Bin "test-writers-python2-bin" { libraries = [ python2Packages.enum ]; } ''
       from enum import Enum
 
 
@@ -73,7 +73,7 @@ let
       print Test.a
     '';
 
-    python3 = writePython3Bin "test_writers_python3_bin" { libraries = [ python3Packages.pyyaml ]; } ''
+    python3 = writePython3Bin "test-writers-python3-bin" { libraries = [ python3Packages.pyyaml ]; } ''
       import yaml
 
       y = yaml.load("""
@@ -84,11 +84,11 @@ let
   };
 
   simple = {
-    bash = writeBash "test_writers_bash" ''
+    bash = writeBash "test-writers-bash" ''
      if [[ "test" == "test" ]]; then echo "success"; fi
     '';
 
-    c = writeC "test_writers_c" { libraries = [ glib.dev ]; } ''
+    c = writeC "test-writers-c" { libraries = [ glib.dev ]; } ''
       #include <gio/gio.h>
       #include <stdio.h>
       int main() {
@@ -106,11 +106,11 @@ let
       }
     '';
 
-    dash = writeDash "test_writers_dash" ''
+    dash = writeDash "test-writers-dash" ''
      test '~' = '~' && echo 'success'
     '';
 
-    haskell = writeHaskell "test_writers_haskell" { libraries = [ haskellPackages.acme-default ]; } ''
+    haskell = writeHaskell "test-writers-haskell" { libraries = [ haskellPackages.acme-default ]; } ''
       import Data.Default
 
       int :: Int
@@ -122,7 +122,7 @@ let
         _ -> print "fail"
     '';
 
-    js = writeJS "test_writers_js" { libraries = [ nodePackages.semver ]; } ''
+    js = writeJS "test-writers-js" { libraries = [ nodePackages.semver ]; } ''
       var semver = require('semver');
 
       if (semver.valid('1.2.3')) {
@@ -132,12 +132,12 @@ let
       }
     '';
 
-    perl = writePerl "test_writers_perl" { libraries = [ perlPackages.boolean ]; } ''
+    perl = writePerl "test-writers-perl" { libraries = [ perlPackages.boolean ]; } ''
       use boolean;
       print "success\n" if true;
     '';
 
-    python2 = writePython2 "test_writers_python2" { libraries = [ python2Packages.enum ]; } ''
+    python2 = writePython2 "test-writers-python2" { libraries = [ python2Packages.enum ]; } ''
       from enum import Enum
 
 
@@ -148,7 +148,7 @@ let
       print Test.a
     '';
 
-    python3 = writePython3 "test_writers_python3" { libraries = [ python3Packages.pyyaml ]; } ''
+    python3 = writePython3 "test-writers-python3" { libraries = [ python3Packages.pyyaml ]; } ''
       import yaml
 
       y = yaml.load("""
@@ -157,21 +157,21 @@ let
       print(y[0]['test'])
     '';
 
-    python2NoLibs = writePython2 "test_writers_python2_no_libs" {} ''
+    python2NoLibs = writePython2 "test-writers-python2-no-libs" {} ''
       print("success")
     '';
 
-    python3NoLibs = writePython3 "test_writers_python3_no_libs" {} ''
+    python3NoLibs = writePython3 "test-writers-python3-no-libs" {} ''
       print("success")
     '';
   };
 
 
   path = {
-    bash = writeBash "test_writers_bash_path" (writeText "test" ''
+    bash = writeBash "test-writers-bash-path" (writeText "test" ''
       if [[ "test" == "test" ]]; then echo "success"; fi
     '');
-    haskell = writeHaskell "test_writers_haskell_path" { libraries = [ haskellPackages.acme-default ]; } (writeText "test" ''
+    haskell = writeHaskell "test-writers-haskell-path" { libraries = [ haskellPackages.acme-default ]; } (writeText "test" ''
       import Data.Default
 
       int :: Int