Add single channel mode feature.

The addition of a single-channel mode implied further modularisation of the component. This commit has broken the component down into the following modules to avoid a huge single source file and to make unit testing easier.

The modules:

- Separation of public and private code
- *types and *defs
- public relay_chn API
- *adapter
- *output
- *run_info
- *core
- *ctl (control)
- *tilt

Closes #957.

include/relay_chn_defs.h

@@ -0,0 +1,24 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Kozmotronik Tech
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+ #pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Config defines for covenient writing */
+#define RELAY_CHN_OPPOSITE_INERTIA_MS CONFIG_RELAY_CHN_OPPOSITE_INERTIA_MS
+#define RELAY_CHN_COUNT CONFIG_RELAY_CHN_COUNT
+#define RELAY_CHN_ENABLE_TILTING CONFIG_RELAY_CHN_ENABLE_TILTING
+
+#if RELAY_CHN_COUNT > 1
+#define RELAY_CHN_ID_ALL RELAY_CHN_COUNT /*!< Special ID to address all channels */
+#endif
+
+#ifdef __cplusplus
+}
+#endif