- Rework InputSystem's Init functions to handle optional domain reloads
- Bypass InitializeInPlayer() "Reset" and "Restore" functions if DRs disabled

Only the first step to getting this working, but enables FEPM support for golden path scenarios.

- Move Reset/Restore state functionality out of InputSystem to the Test assembly (InputTestStateManager.cs)
- Refactor InputManager Init/Dispose to be cleaner and better abstracted:
    * Adds CreateAndInitialize static method
    * Replaces Destroy() with IDisposable implementation
    * InputManager creates "default" InputSettings object if none provided
    * Runtime, Settings, and Metrics fields now private
- Update InitializeInEditor() to incorporate changes
- Update and fix tests

For the most part, the logic should be mostly preserved. InitializeInEditor() has the biggest (logical)
change because Reset() (moved to Tests) contained some actual init calls that needed to be pulled out.
However, we *should* be making the same calls in the same order.

However, this change does seem to "break" some of the OnScreenTests(); they're now unstable.
This will need to be fixed in a later commit.

- Rework the class so it operates as a Singleton (basically how it's being used)
- Move actions get/set implementations from InputSystem to ProjectWideActions class
    * Combine functionality for tighter cohesion despite being an Editor
    * Update #ifefs to allow Player to access some of these members
- Call EnsureInitialized() from Editor init flows to fix the actual bug

Tested using ProjectWideActions sample and verified could move cube when domain reloads disabled.
Ran Package tests (Edit/Play/Player) to verify no (new) failures.

…ns (ISX-1842)

- Make InputSystem static fields private with read-only accessors
- Add InputSystemTestHooks.cs for "Test Hook" operations that need direct access to fields
- Factor out InputSystemObject (and related State) and rename to InputSystemStateManager
- Factor out "dirty asset tracking" functionality to a separate Utility class

Despite touching a bunch of files, this is a low-risk set of changes; functions are moved
to new files and types renamed, but no real changes to functionality.

Validated changes with Edit/Play/Player tests.

- Most ProjectWideAction changes discarded since feature was re-implemented (no longer relevant)
- Recreate InputSystem "Test Hook" for Enabling/Disabling Actions from tests
- Small fixes from unresolved conflicts or bad merges during rebase
- Various formatting changes (to be more consistant)

- Consolidate functionality into DeferBindingResolutionContext class
- Instantiate Context object as a non-static InputManager field exposed via InputManager methods

- Static field (in each class) initialized via RuntimeInitializeOnLoadMethod() hook
- This functionality is a bit clunky and should be refactored but that's out-of-scope for this work

- Add a flag to guard against re-initializing Plugins within PerformDefaultPluginInitialization()
- Refactor SteamSupport to fix Init/Shutdown flows and improve state management
- Refactor PlayerInput's static fields into a single GlobalState struct (matching other classes)
- Move EnhancedTouch static fields into Touch's GlobalState struct
- Minor refactoring of SteamSupport to improve init/cleanp-up flows (especially with tests)

…ts (ISX-1840)

- Consolidate Touchscreen's cached settings into a separate struct
- Rework NativeInputRuntime initialization to (fully) employ Singleton pattern
- Refactor Actions_CanHandleModification TestCase generator to work without Domain Reloads
- Fix Device static fields not getting reset during SimulateDomainReload()

- Rename some variables
- Add update some comments
- Other small tweaks.

# Conflicts:
#	Packages/com.unity.inputsystem/InputSystem/Actions/InputActionMap.cs
#	Packages/com.unity.inputsystem/InputSystem/Actions/InputActionState.cs
#	Packages/com.unity.inputsystem/InputSystem/InputAnalytics.cs
#	Packages/com.unity.inputsystem/InputSystem/InputManager.cs
#	Packages/com.unity.inputsystem/InputSystem/InputSystem.cs
#	Packages/com.unity.inputsystem/Tests/TestFixture/InputTestFixture.cs

…invalid formatting