fix(developer): transform slashes to backslashes in paths in Package Editor

[mcdurdin]

When loading package files generated by kmc or edited on non-Windows systems, the Package Editor will now convert any forward slashes in the path to backslashes. This is necessary because the path manipulation functions in Keyman Developer work only with backslashes.

Fixes: #14719
Build-bot: skip release:developer

User Testing

TEST_CLONE: Try to clone a local keyboard project in Keyman Developer, e.g. obolo_chwerty from the keyboard repository. Use the new keyboard project id my_cloned_keyboard. Verify that the cloned .kps file uses forward slashes in file paths, such as <Name>../build/my_cloned_keyboard.kmx</Name>. Open this package file in the package editor, and verify that the Keyboard ID matches my_cloned_keyboard, and that the package compiles successfully.

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• ✅ TEST_CLONE (PASSED) (notes)

Test Artifacts

• Developer
  • Keyman Developer
  • Compiler Regression Tests
  • Keyman Developer (old PRs)
  • kmcomp.zip
  • kmcomp.zip (old PRs)
• Keyboards
  • Test Keyboards

[ermshiperete]

LGTM

[Meng-Heng]

Test Results

Windows 10 Bootcamp, Keyman Developer v19.0.116-alpha-test-14721
The results are as followed:

Prerequisites

1. Fetch & Pull keyboards repo for latest

• TEST_CLONE (PASSED):

1. Open Keyman Developer > Go to Project > New Project > Clone local project
2. Specified "Source project filename" to release/o/obolo_chwerty/obolo_chwerty.kpj and "New Project ID" as my_cloned_keyboard:
   
3. Compile my_cloned_keyboard.kmn successfully
4. Compile my_cloned_keyboard.kps successfully
5. Verified: ID is my_cloned_keyboard

   <Keyboard>
    <ID>my_cloned_keyboard</ID>
    <OSKFont>..\external\shared\fonts\noto\Latn\NotoSans-Regular.ttf</OSKFont>
    <DisplayFont>..\external\shared\fonts\noto\Latn\NotoSans-Regular.ttf</DisplayFont>
    <Languages>
      <Language ID="ann">Obolo (Andoni)</Language>
    </Languages>
   </Keyboard>
   

6. Verified: All the paths use backward slashes in the Source tab of Keyman Developer. Once open in a different text editor, e.g. VS Code, the paths use forward slashes.

   <File>
     <Name>../build/my_cloned_keyboard.kvk</Name>
     ...
   <File> 
     <Name>../build/my_cloned_keyboard.kmx</Name>
   

[keyman-server]

Changes in this pull request will be available for download in Keyman version 19.0.119-alpha