Move some functions out of 'api/utils/common.py' (#10948)

### What problem does this PR solve?

as title.

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

api/utils/common.py

@@ -14,12 +14,6 @@
 #  limitations under the License.
 #
 
-import threading
-import subprocess
-import sys
-import os
-import logging
-
 def string_to_bytes(string):
     return string if isinstance(
         string, bytes) else string.encode(encoding="utf-8")
@@ -28,70 +22,3 @@ def string_to_bytes(string):
 def bytes_to_string(byte):
     return byte.decode(encoding="utf-8")
 
-
-def convert_bytes(size_in_bytes: int) -> str:
-    """
-    Format size in bytes.
-    """
-    if size_in_bytes == 0:
-        return "0 B"
-
-    units = ['B', 'KB', 'MB', 'GB', 'TB', 'PB']
-    i = 0
-    size = float(size_in_bytes)
-
-    while size >= 1024 and i < len(units) - 1:
-        size /= 1024
-        i += 1
-
-    if i == 0 or size >= 100:
-        return f"{size:.0f} {units[i]}"
-    elif size >= 10:
-        return f"{size:.1f} {units[i]}"
-    else:
-        return f"{size:.2f} {units[i]}"
-
-
-def once(func):
-    """
-    A thread-safe decorator that ensures the decorated function runs exactly once,
-    caching and returning its result for all subsequent calls. This prevents
-    race conditions in multi-threaded environments by using a lock to protect
-    the execution state.
-
-    Args:
-        func (callable): The function to be executed only once.
-
-    Returns:
-        callable: A wrapper function that executes `func` on the first call
-                  and returns the cached result thereafter.
-
-    Example:
-        @once
-        def compute_expensive_value():
-            print("Computing...")
-            return 42
-
-        # First call: executes and prints
-        # Subsequent calls: return 42 without executing
-    """
-    executed = False
-    result = None
-    lock = threading.Lock()
-    def wrapper(*args, **kwargs):
-        nonlocal executed, result
-        with lock:
-            if not executed:
-                executed = True
-                result = func(*args, **kwargs)
-        return result
-    return wrapper
-
-@once
-def pip_install_torch():
-    device = os.getenv("DEVICE", "cpu")
-    if device=="cpu":
-        return
-    logging.info("Installing pytorch")
-    pkg_names = ["torch>=2.5.0,<3.0.0"]
-    subprocess.check_call([sys.executable, "-m", "pip", "install", *pkg_names])