[lsm6ds] Restructure component with _base, _i2c, _spi pattern

Major restructure to follow ESPHome conventions for multi-interface components:

Component Structure Changes:
- Renamed lsm6ds/ to lsm6ds_base/ to follow _base naming convention
- Created lsm6ds_i2c/ for I2C interface implementation
- Created lsm6ds_spi/ for SPI interface implementation
- Both interfaces use AUTO_LOAD to automatically include base component
- Updated C++ namespaces to match component folder names (lsm6ds_base, lsm6ds_i2c, lsm6ds_spi)

Features:
- Support for LSM6DSOX, LSM6DS3TR-C, LSM6DSO32 variants
- Full 3-axis accelerometer and gyroscope support
- Temperature sensor support
- Configurable ranges: Accel (2G-16G), Gyro (125-2000 DPS)
- Configurable output data rate (12.5Hz - 6.66kHz)
- Two usage patterns: all-in-one and hub+sensor platform

Implementation Details:
- Base component (lsm6ds_base) contains shared code and abstract LSM6DSComponent class
- I2C variant implements LSM6DSI2CDevice with I2C read/write methods
- SPI variant implements LSM6DSSPIDevice with SPI read/write methods (MSB-based protocol)
- Both variants support optional sensor.py for hub+sensor pattern
- Added README_EXAMPLE.md files with usage examples for both interfaces
- Added component test files for validation

Documentation:
- Added COMPONENT_STRUCTURE.md explaining architecture and usage patterns
- Included example configurations for both I2C and SPI
- Documented all configuration options and sensor variants

tests/components/lsm6ds/common.yaml

@@ -0,0 +1,31 @@
+lsm6ds_i2c:
+  id: lsm6ds_i2c_hub
+
+lsm6ds_spi:
+  id: lsm6ds_spi_hub
+  cs_pin: GPIO5
+
+sensor:
+  - platform: lsm6ds
+    lsm6ds_id: lsm6ds_i2c_hub
+    accel_x:
+      name: "I2C Accel X"
+    accel_y:
+      name: "I2C Accel Y"
+    accel_z:
+      name: "I2C Accel Z"
+    gyro_x:
+      name: "I2C Gyro X"
+    gyro_y:
+      name: "I2C Gyro Y"
+    gyro_z:
+      name: "I2C Gyro Z"
+    temperature:
+      name: "I2C Temperature"
+
+  - platform: lsm6ds
+    lsm6ds_id: lsm6ds_spi_hub
+    accel_x:
+      name: "SPI Accel X"
+    gyro_x:
+      name: "SPI Gyro X"

tests/components/lsm6ds/test.esp32-ard.yaml

@@ -0,0 +1,5 @@
+packages:
+  i2c: !include ../../test_build_components/common/i2c/esp32-ard.yaml
+  spi: !include ../../test_build_components/common/spi/esp32-ard.yaml
+
+<<: !include common.yaml

tests/components/lsm6ds/test.esp32-idf.yaml

@@ -0,0 +1,5 @@
+packages:
+  i2c: !include ../../test_build_components/common/i2c/esp32-idf.yaml
+  spi: !include ../../test_build_components/common/spi/esp32-idf.yaml
+
+<<: !include common.yaml

tests/lsm6ds_test.yaml

@@ -0,0 +1,43 @@
+esphome:
+  name: lsm6ds_test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: arduino
+
+i2c:
+  sda: 21
+  scl: 22
+
+spi:
+  clk_pin: 18
+  mosi_pin: 23
+  miso_pin: 19
+
+lsm6ds_i2c:
+  id: my_lsm6ds_i2c
+  address: 0x6A
+
+lsm6ds_spi:
+  id: my_lsm6ds_spi
+  cs_pin: 5
+
+sensor:
+  - platform: lsm6ds
+    lsm6ds_id: my_lsm6ds_i2c
+    accel_x:
+      name: "I2C Accel X"
+    gyro_x:
+      name: "I2C Gyro X"
+    temperature:
+      name: "I2C Temp"
+
+  - platform: lsm6ds
+    lsm6ds_id: my_lsm6ds_spi
+    accel_x:
+      name: "SPI Accel X"
+    gyro_x:
+      name: "SPI Gyro X"
+    temperature:
+      name: "SPI Temp"