KeyFileUtil: Generics with GLib.Value

[ryonakano]

Generics does not seem to support string[] so use GLib.Value instead.

../src/Model/DesktopFile.vala:140.63-140.70: error: Arrays are not supported as generic type arguments
  140 |             string[]? categories = Util.KeyFileUtil.get_value<string[]> (keyfile_dirty, KeyFileDesktop.KEY_CATEGORIES, Util.KeyFileUtil.get_strv);
      |                                                               ^~~~~~~~
../src/Model/DesktopFile.vala:154.40-154.47: error: Arrays are not supported as generic type arguments
  154 |             Util.KeyFileUtil.set_value<string[]> (keyfile_dirty, KeyFileDesktop.KEY_CATEGORIES, categories, Util.KeyFileUtil.set_strv);
      |                                        ^~~~~~~~
../src/Model/DesktopFile.vala:163.61-163.68: error: Arrays are not supported as generic type arguments
  163 |             string[]? keywords = Util.KeyFileUtil.get_value<string[]> (keyfile_dirty, Util.KeyFileUtil.KEY_KEYWORDS, Util.KeyFileUtil.get_strv);
      |                                                             ^~~~~~~~
../src/Model/DesktopFile.vala:177.40-177.47: error: Arrays are not supported as generic type arguments
  177 |             Util.KeyFileUtil.set_value<string[]> (keyfile_dirty, Util.KeyFileUtil.KEY_KEYWORDS, keywords, Util.KeyFileUtil.set_strv);
      |                                        ^~~~~~~~
glib-2.0.vapi:35.1-35.18: error: The type `bool' doesn't declare a GValue take function
   35 | public struct bool {
      | ^~~~~~~~~~~~~~~~~~
Compilation failed: 5 error(s), 0 warning(s)
[2/15] Generating src/valadoc with a custom command
Succeeded - 0 warning(s)
ninja: build stopped: subcommand failed.