Define an env for controlling UVloop (#58442)

> Briefly describe what this PR accomplishes and why it's needed.

Our serve ingress keeps running into below error related to `uvloop`
under heavy load
```
File descriptor 97 is used by transport
```
The uvloop team have a
[PR](MagicStack/uvloop#646) to fix it, but seems
like no one is working on it

One of workaround mentioned in the
([PR](MagicStack/uvloop#646 (comment)))
is to just turn off uvloop .
We tried it in our env and didn't see any major performance difference
Hence as part of this PR, we are defining a new env for controlling
UVloop

Signed-off-by: jugalshah291 <[email protected]>

Author: jugalshah291

python/ray/_private/async_compat.py

@@ -6,23 +6,25 @@
 import inspect
 from functools import lru_cache
 
+from ray._private.ray_constants import env_bool
+
 try:
     import uvloop
 except ImportError:
     uvloop = None
 
 
 def get_new_event_loop():
-    """Construct a new event loop. Ray will use uvloop if it exists"""
-    if uvloop:
+    """Construct a new event loop. Ray will use uvloop if it exists and is enabled"""
+    if uvloop and env_bool("RAY_USE_UVLOOP", True):
         return uvloop.new_event_loop()
     else:
         return asyncio.new_event_loop()
 
 
 def try_install_uvloop():
-    """Installs uvloop as event-loop implementation for asyncio (if available)"""
-    if uvloop:
+    """Installs uvloop as event-loop implementation for asyncio (if available and enabled)"""
+    if uvloop and env_bool("RAY_USE_UVLOOP", True):
         uvloop.install()
     else:
         pass