FIX: save and reset input action asset (ISX-1525, ISX-1483, ISX-1559)

[ritamerkl]

Description

Three tickets around saving/auto-saving and reset the input action asset including a dialog (showing up if no auto-save is enabled and the editor window is closed) are solved in this PR. You can find them here: ISX-1525, ISX-1483, ISX-1559.

Changes made

fixed:

• reset dialog properly if changes got discarded

added:

• dialog that shows up on closing the editor window and auto-save is disabled
• dirty asset editor window if auto-save disabled and asset has unsaved changes

Checklist

Before review:

• Changelog entry added.
  • Explains the change in Changed, Fixed, Added sections.
  • For API change contains an example snippet and/or migration example.
  • FogBugz ticket attached, example ([case %number%](https://issuetracker.unity3d.com/issues/...)).
  • FogBugz is marked as "Resolved" with next release version correctly set.
• Tests added/changed, if applicable.
  • Functional tests Area_CanDoX, Area_CanDoX_EvenIfYIsTheCase, Area_WhenIDoX_AndYHappens_ThisIsTheResult.
  • Performance tests.
  • Integration tests.
• Docs for new/changed API's.
  • Xmldoc cross references are set correctly.
  • Added explanation how the API works.
  • Usage code examples added.
  • The manual is updated, if needed.

During merge:

• Commit message for squash-merge is prefixed with one of the list:
  • NEW: ___.
  • FIX: ___.
  • DOCS: ___.
  • CHANGE: ___.
  • RELEASE: 1.1.0-preview.3.

[lyndon-unity]

Some questions and suggestions above

[lyndon-unity]

Saving and auto saving seems to work as expected for me.
This update looks good