feat(mouse): Add mouse move and scroll support (#2477)

* feat(mouse): Add mouse move and scroll support

    * Use Zephyr input subsystem for all pointers.
    * Input processors for modifying events, e.g. scaling, swapping
      codes, temporary (mouse) layers, etc.
    * Mouse move/scroll behaviors.
    * Infrastructure in place for physical pointer input devices.

* feat: Add input split support.

* docs: Add initial pointer docs.

---------

Co-authored-by: Cem Aksoylar <caksoylar@users.noreply.github.com>
Co-authored-by: Alexander Krikun <krikun98@gmail.com>
Co-authored-by: Robert U <urob@users.noreply.github.com>
Co-authored-by: Shawn Meier <ftc@users.noreply.github.com>
Co-authored-by: Chris Andreae <chris@andreae.gen.nz>
Co-authored-by: Anant Thazhemadam <47104651+thazhemadam@users.noreply.github.com>
Co-authored-by: Erik Tollerud <erik.tollerud@gmail.com>
Co-authored-by: Nicolas Munnich <98408764+Nick-Munnich@users.noreply.github.com>

app/src/pointing/Kconfig

@@ -0,0 +1,75 @@
+# Copyright (c) 2024 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+menu "Pointing Options"
+
+# Deprecated old config, kept for backwards compat
+config ZMK_MOUSE
+    bool "(Deprecated) Mouse Support"
+
+config ZMK_POINTING
+    bool "Pointing Device Support"
+    default y if ZMK_MOUSE
+    select INPUT
+    select INPUT_THREAD_PRIORITY_OVERRIDE
+
+if ZMK_POINTING
+
+# Needed for anyone using gpio-keys for things like soft-off setup.
+config INPUT_GPIO_KEYS
+    default n
+
+config INPUT_THREAD_STACK_SIZE
+    default 1024 if ZMK_SPLIT && !ZMK_SPLIT_ROLE_CENTRAL
+
+if !ZMK_SPLIT || ZMK_SPLIT_ROLE_CENTRAL
+
+config ZMK_POINTING_SMOOTH_SCROLLING
+    bool "Smooth Scrolling"
+    help
+      Enable smooth scrolling, with hosts that support HID Resolution Multipliers
+
+config ZMK_INPUT_LISTENER
+    bool "Input listener for processing input events in the system"
+    default y
+    depends on DT_HAS_ZMK_INPUT_LISTENER_ENABLED
+
+
+config ZMK_INPUT_PROCESSOR_TEMP_LAYER
+    bool "Temporary Layer Input Processor"
+    default y
+    depends on DT_HAS_ZMK_INPUT_PROCESSOR_TEMP_LAYER_ENABLED
+
+endif
+
+config ZMK_INPUT_PROCESSOR_TRANSFORM
+    bool "Transform Input Processor"
+    default y
+    depends on DT_HAS_ZMK_INPUT_PROCESSOR_TRANSFORM_ENABLED
+
+config ZMK_INPUT_PROCESSOR_SCALER
+    bool "Scaling Input Processor"
+    default y
+    depends on DT_HAS_ZMK_INPUT_PROCESSOR_SCALER_ENABLED
+
+config ZMK_INPUT_PROCESSOR_CODE_MAPPER
+    bool "Code Mapper Input Processor"
+    default y
+    depends on DT_HAS_ZMK_INPUT_PROCESSOR_CODE_MAPPER_ENABLED
+
+config ZMK_INPUT_SPLIT
+    bool "Split input support"
+    default y
+    depends on DT_HAS_ZMK_INPUT_SPLIT_ENABLED && ZMK_SPLIT
+
+if ZMK_INPUT_SPLIT
+
+config ZMK_INPUT_SPLIT_INIT_PRIORITY
+    int "Input Split initialization priority"
+    default INPUT_INIT_PRIORITY
+
+endif # ZMK_INPUT_SPLIT
+
+endif # ZMK_POINTING
+
+endmenu # Mouse Options