feat: Add support for VS Code and JetBrains Gateway via SSH (#956)

* Improve CLI documentation

* feat: Allow workspace resources to attach multiple agents

This enables a "kubernetes_pod" to attach multiple agents that
could be for multiple services. Each agent is required to have
a unique name, so SSH syntax is:

`coder ssh <workspace>.<agent>`

A resource can have zero agents too, they aren't required.

* Add tree view

* Improve table UI

* feat: Allow workspace resources to attach multiple agents

This enables a "kubernetes_pod" to attach multiple agents that
could be for multiple services. Each agent is required to have
a unique name, so SSH syntax is:

`coder ssh <workspace>.<agent>`

A resource can have zero agents too, they aren't required.

* Rename `tunnel` to `skip-tunnel`

This command was `true` by default, which causes
a confusing user experience.

* Add disclaimer about editing templates

* Add help to template create

* Improve workspace create flow

* Add end-to-end test for config-ssh

* Improve testing of config-ssh

* Fix workspace list

* feat: Add support for VS Code and JetBrains Gateway via SSH

This fixes various bugs that made this not work:
- Incorrect max message size in `peer`
- Incorrect reader buffer size in `peer`
- Lack of SFTP support in `agent`
- Lack of direct-tcpip support in `agent`
- Misuse of command from session. It should always use the shell
- Blocking on SSH session, only allowing one at a time

Fixes #833 too.

* Fix config-ssh command with socat

.github/workflows/coder.yaml

@@ -158,6 +158,10 @@ jobs:
           terraform_version: 1.1.2
           terraform_wrapper: false
 
+      - name: Install socat
+        if: runner.os == 'Linux'
+        run: sudo apt-get install -y socat
+
       - name: Test with Mock Database
         shell: bash
         env: