[RegPreview] Various improvements on how files are saved

[htcfreek]

Summary of the Pull Request

This PR implements various fixes and improvements into RegistryPreview for saving files:

1. Adds an unsaved file indicator in the title bar like in Notepad. (As indicator we show the * character before the file title.)
2. The save button behaves like a "save as" button, if the file does not exist on disk like in Notepad. (Without fix when running as non-admin you get an access denied error message.)
3. If the app gets closed without saving and the file does not exist on disk, then the user is now asked for the path. (Fixes crash on clicking save button while closing the app.)
4. Failed save actions are handled now correctly on dirty closing, opening files and all other actions that require saving the current state. They will stop the process.
5. A fix for an incorrect enabled state of the save button after opening, reloading and saving a file.
6. Reuse file name on save as button, if known. Otherwise use "new file" template name like in Notepad.
7. Fix an app crash if you click the window's close button a second time while the "Should save?" dialog is opened.
8. Added an reload dialog in case of unsaved changes.

PR Checklist

• Closes: [RegistryPreview] Crash clicking save on message when closing #36876, [Registry Preview] Save as behavior on save button for temp file #36875
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

Local test build.

[randyrants]

Up to recently, the enablement of the Save button was the indicator that the file was dirty or not. With this new functionality in place, to add a * to the title of the toolbar, I would think it makes sense to move all settings of saveButton.IsEnabled into the UpdateUnsavedFileIndicator method, so no one forgets to set one versus the other in the future.

JM2C.

[htcfreek]

@randyrants
That makes so much sense.

[Copilot]

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

[htcfreek]

@crutkas
Can we have a "in for .92" label for this?

[crutkas]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[yeelam-gordon]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[yeelam-gordon]

@htcfreek, I just rebased your branch with main. There are many conflicts with the change probably you made 2 months ago.
Please see the rebase itself make sense.

[yeelam-gordon]

Try out locally, the functionality looks great ;-)