feat: support configurable web terminal rendering (#10095)

* feat: support configurable web terminal rendering

- Added a deployment option for configuring web terminal rendering.
  Valid values are 'webgl', 'canvas', and 'dom'.

cli/testdata/coder_server_--help.golden

@@ -66,6 +66,10 @@ Clients include the coder cli, vs code extension, and the web UI.
       --ssh-hostname-prefix string, $CODER_SSH_HOSTNAME_PREFIX (default: coder.)
           The SSH deployment prefix is used in the Host of the ssh config.
 
+      --web-terminal-renderer string, $CODER_WEB_TERMINAL_RENDERER (default: canvas)
+          The renderer to use when opening a web terminal. Valid values are
+          'canvas', 'webgl', or 'dom'.
+
 CONFIG OPTIONS: 
 Use a YAML configuration file when your server launch become unwieldy.
 

cli/testdata/server-config.yaml.golden

@@ -411,6 +411,10 @@ client:
   # incorrectly can break SSH to your deployment, use cautiously.
   # (default: <unset>, type: string-array)
   sshConfigOptions: []
+  # The renderer to use when opening a web terminal. Valid values are 'canvas',
+  # 'webgl', or 'dom'.
+  # (default: canvas, type: string)
+  webTerminalRenderer: canvas
 # Support links to display in the top right drop down menu.
 # (default: <unset>, type: struct[[]codersdk.LinkConfig])
 supportLinks: []