The `SingleTailnet` behavior only checked to see if the `MultiAgent` was
closed, but the websocket error was not being propogated into the
`MultiAgent`, causing it to never be swapped for a new working one.
Fixes https://github.com/coder/coder/issues/11401
Before:
```
Coder Workspace Proxy v0.0.0-devel+85ff030 - Your Self-Hosted Remote Development Platform
Started HTTP listener at http://0.0.0.0:3001
View the Web UI: http://127.0.0.1:3001
==> Logs will stream in below (press ctrl+c to gracefully exit):
2024-01-04 20:11:56.376 [warn] net.workspace-proxy.servertailnet: broadcast server node to agents ...
error= write message:
github.com/coder/coder/v2/enterprise/wsproxy/wsproxysdk.(*remoteMultiAgentHandler).writeJSON
/home/coder/coder/enterprise/wsproxy/wsproxysdk/wsproxysdk.go:524
- failed to write msg: WebSocket closed: failed to read frame header: EOF
```
After:
```
Coder Workspace Proxy v0.0.0-devel+12f1878 - Your Self-Hosted Remote Development Platform
Started HTTP listener at http://0.0.0.0:3001
View the Web UI: http://127.0.0.1:3001
==> Logs will stream in below (press ctrl+c to gracefully exit):
2024-01-04 20:26:38.545 [warn] net.workspace-proxy.servertailnet: multiagent closed, reinitializing
2024-01-04 20:26:38.546 [erro] net.workspace-proxy.servertailnet: reinit multi agent ...
error= dial coordinate websocket:
github.com/coder/coder/v2/enterprise/wsproxy/wsproxysdk.(*Client).DialCoordinator
/home/coder/coder/enterprise/wsproxy/wsproxysdk/wsproxysdk.go:454
- failed to WebSocket dial: failed to send handshake request: Get "http://127.0.0.1:3000/api/v2/workspaceproxies/me/coordinate": dial tcp 127.0.0.1:3000: connect: connection refused
2024-01-04 20:26:38.587 [erro] net.workspace-proxy.servertailnet: reinit multi agent ...
error= dial coordinate websocket:
github.com/coder/coder/v2/enterprise/wsproxy/wsproxysdk.(*Client).DialCoordinator
/home/coder/coder/enterprise/wsproxy/wsproxysdk/wsproxysdk.go:454
- failed to WebSocket dial: failed to send handshake request: Get "http://127.0.0.1:3000/api/v2/workspaceproxies/me/coordinate": dial tcp 127.0.0.1:3000: connect: connection refusedhandshake request: Get "http://127.0.0.1:3000/api/v2/workspaceproxies/me/coordinate": dial tcp 127.0.0.1:3000: connect: connection refused
2024-01-04 20:26:40.446 [info] net.workspace-proxy.servertailnet: successfully reinitialized multiagent agents=0 took=1.900892615s
```
* chore: add /v2 to import module path
go mod requires semantic versioning with versions greater than 1.x
This was a mechanical update by running:
```
go install github.com/marwan-at-work/mod/cmd/mod@latest
mod upgrade
```
Migrate generated files to import /v2
* Fix gen
