chore: update change log to v2.10.0 and install docs for release channels (#12863)

* 2.10.0 changelog

* updated install docs for mainline/stable releases

* make fmt

* cpp icon -> C++

* added disclaimer on MAX_TTL, support bundle info

* 'release schedule'

* lowercase mainline

* Agent OOM protection info

* minor tweak

docs/install/kubernetes.md

@@ -7,6 +7,15 @@ You'll also want to install the
 [latest version of Coder](https://github.com/coder/coder/releases/latest)
 locally in order to log in and manage templates.
 
+> Coder supports two release channels: mainline for the true latest version of
+> Coder, and stable for large enterprise deployments. Before installing your
+> control plane via Helm, please read the [Releases](./releases.md) document to
+> identify the best-suited release for your team, then specify the version using
+> Helm's `--version` flag.
+
+> The version flags for both stable and mainline are automatically filled in
+> this page.
+
 ## Install Coder with Helm
 
 1. Create a namespace for Coder, such as `coder`:
@@ -112,10 +121,22 @@ locally in order to log in and manage templates.
 
 1. Run the following command to install the chart in your cluster.
 
+   For the **mainline** Coder release:
+
    ```shell
    helm install coder coder-v2/coder \
        --namespace coder \
-       --values values.yaml
+       --values values.yaml \
+       --version 2.10.0
+   ```
+
+   For the **stable** Coder release:
+
+   ```shell
+   helm install coder coder-v2/coder \
+       --namespace coder \
+       --values values.yaml \
+       --version 2.9.1
    ```
 
    You can watch Coder start up by running `kubectl get pods -n coder`. Once