[lsm6ds_base] Rename C++ files to include _base suffix

Renamed the C++ implementation files to match the component folder naming:
- lsm6ds.h -> lsm6ds_base.h
- lsm6ds.cpp -> lsm6ds_base.cpp

Updated all includes:
- lsm6ds_base/lsm6ds_base.cpp: Updated self-include
- lsm6ds_i2c/lsm6ds_i2c.h: Updated to include lsm6ds_base.h
- lsm6ds_spi/lsm6ds_spi.h: Updated to include lsm6ds_base.h

Fixed test file:
- tests/lsm6ds_test.yaml: Updated sensor platforms to use lsm6ds_i2c and lsm6ds_spi

This ensures all files follow consistent naming conventions with the _base suffix.

esphome/components/lsm6ds_base/lsm6ds_base.cpp

@@ -1,4 +1,4 @@
-#include "lsm6ds.h"
+#include "lsm6ds_base.h"
 #include "esphome/core/log.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/hal.h"

esphome/components/lsm6ds_i2c/lsm6ds_i2c.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "esphome/components/i2c/i2c.h"
-#include "esphome/components/lsm6ds_base/lsm6ds.h"
+#include "esphome/components/lsm6ds_base/lsm6ds_base.h"
 
 namespace esphome {
 namespace lsm6ds_i2c {

esphome/components/lsm6ds_spi/lsm6ds_spi.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "esphome/components/lsm6ds_base/lsm6ds.h"
+#include "esphome/components/lsm6ds_base/lsm6ds_base.h"
 #include "esphome/components/spi/spi.h"
 
 namespace esphome {