Merge the duplicated event loop how-to pages

Asyncio-Integration.md and Event-Loop-Integration.md were near-identical:
same title, 803 and 796 lines, 25 of 28 code blocks and 69 of 77 headings
byte-identical. Neither was a superset, so deleting either would have
lost content: one carried Part 0 on same-thread asyncio mode and the
comparison table, the other carried simulation mode and the matching
CspEventLoop constructor and set_simulation_time_range reference.

Fold both sets into Event-Loop-Integration.md, whose filename matches the
title the two shared, and drop the other along with its sidebar entry.
Every heading and code block from the deleted page is present in the
merged one.

Async.md is a different document, about the adapters rather than the loop,
and shares no code with either. It restated how same-thread mode works, so
that is now a link to the page that owns the topic.

Signed-off-by: Tim Paine <3105306+timkpaine@users.noreply.github.com>

Author: timkpaine

docs/wiki/_Sidebar.md

@@ -37,7 +37,6 @@ Notes for editors:
   - [Write Output Adapters](Write-Output-Adapters)
 - [Profile CSP Code](Profile-CSP-Code)
 - [Event Loop Integration](Event-Loop-Integration)
-- [Asyncio Integration](Asyncio-Integration)
 
 **References**
 

docs/wiki/dev-guides/Architecture.md

@@ -543,4 +543,4 @@ ______________________________________________________________________
 - [CSP Node concepts](../concepts/CSP-Node.md) - Node anatomy and lifecycle hooks
 - [Execution Modes](../concepts/Execution-Modes.md) - Simulation vs realtime
 - [Adapters](../concepts/Adapters.md) - Writing custom adapters
-- [Asyncio Integration](../how-tos/Asyncio-Integration.md) - Using CSP with asyncio
+- [Asyncio Integration](../how-tos/Event-Loop-Integration.md) - Using CSP with asyncio

docs/wiki/how-tos/Async.md

@@ -89,15 +89,7 @@ To use the legacy background thread mode instead:
 csp.run(my_graph, realtime=True, endtime=timedelta(seconds=5), asyncio_on_thread=True)
 ```
 
-To check if you're in asyncio mode:
-
-```python
-from csp.impl.async_adapter import is_csp_asyncio_mode, get_csp_asyncio_loop
-
-if is_csp_asyncio_mode():
-    loop = get_csp_asyncio_loop()
-    print(f"Running in CSP asyncio mode on {loop}")
-```
+See [Event Loop Integration](Event-Loop-Integration.md) for how this mode works, how to detect it from inside a node, and its requirements.
 
 ### Option 3: Custom Event Loop