Support GET for /ingester/shutdown (grafana#11477)

**Which issue(s) this PR fixes**:
Fixes grafana#11431 

**Checklist**
- [X] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [X] Documentation added
- [ ] Tests updated
- [x] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md`
- [ ] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
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- [ ] If the change is deprecating or removing a configuration option,
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---------

Signed-off-by: Michel Hollands <[email protected]>

CHANGELOG.md

@@ -6,6 +6,8 @@
 
 ##### Enhancements
 
+* [11363](https://github.com/grafana/loki/pull/11477) **MichelHollands**: support GET for /ingester/shutdown
+* [11363](https://github.com/grafana/loki/pull/11363) **kavirajk**: bugfix(memcached): Make memcached batch fetch truely context aware.
 * [11319](https://github.com/grafana/loki/pull/11319) **someStrangerFromTheAbyss**: Helm: Add extraContainers to the write pods.
 * [11243](https://github.com/grafana/loki/pull/11243) **kavirajk**: Inflight-logging: Add extra metadata to inflight requests logging.
 * [11110](https://github.com/grafana/loki/pull/11003) **MichelHollands**: Change the default of the `metrics-namespace` flag to 'loki'.

docs/sources/reference/api.md

@@ -988,7 +988,7 @@ This API endpoint is usually used by Kubernetes-specific scale down automations
 ## Flush in-memory chunks and shut down
 
 ```
-POST /ingester/shutdown
+GET, POST /ingester/shutdown
 ```
 
 `/ingester/shutdown` triggers a shutdown of the ingester and notably will _always_ flush any in memory chunks it holds.

pkg/loki/modules.go

@@ -579,7 +579,7 @@ func (t *Loki) initIngester() (_ services.Service, err error) {
 	t.Server.HTTP.Methods("POST", "GET", "DELETE").Path("/ingester/prepare_shutdown").Handler(
 		httpMiddleware.Wrap(http.HandlerFunc(t.Ingester.PrepareShutdown)),
 	)
-	t.Server.HTTP.Methods("POST").Path("/ingester/shutdown").Handler(
+	t.Server.HTTP.Methods("POST", "GET").Path("/ingester/shutdown").Handler(
 		httpMiddleware.Wrap(http.HandlerFunc(t.Ingester.ShutdownHandler)),
 	)
 	return t.Ingester, nil