[npu] change device to accelerator api (#5239)

* update accelerator

* fix timer

* fix amp

* update

* fix

* update bug

* add error raise

* fix autocast

* fix set device

* remove doc accelerator

* update doc

* update doc

* update doc

* use nullcontext

* update cpu

* update null context

* change time limit for example

* udpate

* update

* update

* update

* [npu] polish accelerator code

---------

Co-authored-by: Xuanlei Zhao <xuanlei.zhao@gmail.com>
Co-authored-by: zxl <43881818+oahzxl@users.noreply.github.com>

colossalai/utils/timer.py

@@ -3,7 +3,7 @@
 import time
 from typing import Tuple
 
-from .device import synchronize
+from colossalai.accelerator import get_accelerator
 
 
 class Timer:
@@ -21,13 +21,13 @@ class Timer:
 
     @property
     def current_time(self) -> float:
-        synchronize()
+        get_accelerator().synchronize()
         return time.time()
 
     def start(self):
         """Firstly synchronize cuda, reset the clock and then start the timer."""
         self._elapsed = 0
-        synchronize()
+        get_accelerator().synchronize()
         self._start_time = time.time()
         self._started = True
 
@@ -44,7 +44,7 @@ class Timer:
         Returns:
             int: Start-stop interval.
         """
-        synchronize()
+        get_accelerator().synchronize()
         end_time = time.time()
         elapsed = end_time - self._start_time
         if keep_in_history: