Cleanly shutdown SynapseHomeServer object (#18828)

This PR aims to allow for a clean shutdown of the `SynapseHomeServer`
object so that it can be fully deleted and cleaned up by garbage
collection without shutting down the entire python process.

Fix https://github.com/element-hq/synapse-small-hosts/issues/50

### Pull Request Checklist

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before submitting your pull request -->

* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct (run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))

---------

Co-authored-by: Eric Eastwood <erice@element.io>

synmark/suites/logging.py

@@ -86,7 +86,9 @@ async def main(reactor: ISynapseReactor, loops: int) -> float:
     hs_config = Config()
 
     # To be able to sleep.
-    clock = Clock(reactor, server_name=hs_config.server.server_name)
+    # Ignore linter error here since we are running outside of the context of a
+    # Synapse `HomeServer`.
+    clock = Clock(reactor, server_name=hs_config.server.server_name)  # type: ignore[multiple-internal-clocks]
 
     errors = StringIO()
     publisher = LogPublisher()

synmark/suites/lrucache.py

@@ -23,14 +23,19 @@ from pyperf import perf_counter
 
 from synapse.types import ISynapseReactor
 from synapse.util.caches.lrucache import LruCache
+from synapse.util.clock import Clock
 
 
 async def main(reactor: ISynapseReactor, loops: int) -> float:
     """
     Benchmark `loops` number of insertions into LruCache without eviction.
     """
+    # Ignore linter error here since we are running outside of the context of a
+    # Synapse `HomeServer`.
     cache: LruCache[int, bool] = LruCache(
-        max_size=loops, server_name="synmark_benchmark"
+        max_size=loops,
+        clock=Clock(reactor, server_name="synmark_benchmark"),  # type: ignore[multiple-internal-clocks]
+        server_name="synmark_benchmark",
     )
 
     start = perf_counter()

synmark/suites/lrucache_evict.py

@@ -23,6 +23,7 @@ from pyperf import perf_counter
 
 from synapse.types import ISynapseReactor
 from synapse.util.caches.lrucache import LruCache
+from synapse.util.clock import Clock
 
 
 async def main(reactor: ISynapseReactor, loops: int) -> float:
@@ -30,8 +31,12 @@ async def main(reactor: ISynapseReactor, loops: int) -> float:
     Benchmark `loops` number of insertions into LruCache where half of them are
     evicted.
     """
+    # Ignore linter error here since we are running outside of the context of a
+    # Synapse `HomeServer`.
     cache: LruCache[int, bool] = LruCache(
-        max_size=loops // 2, server_name="synmark_benchmark"
+        max_size=loops // 2,
+        clock=Clock(reactor, server_name="synmark_benchmark"),  # type: ignore[multiple-internal-clocks]
+        server_name="synmark_benchmark",
     )
 
     start = perf_counter()