Add devtunnel connection for debugger jobs

[rentziass]

This PR adds remote debugger connectivity to the runner via Dev Tunnels. The runner now deserializes the DebuggerTunnel payload (tunnel ID, cluster, host token, port) from the job message, binds the DAP server to the tunnel-provided port, and starts a Dev Tunnel relay so remote DAP clients can connect. The DAP port is now mandated by the backend for two reasons:

• the token the runner gets doesn't allow it to manage the dev tunnel (and for example add other ports)
• forcing the runner to use port 4711 (failing the job if not available) makes sure we don't relay something that isn't the DAP server over Dev Tunnel

Since we're adding more debugger configuration this also changes the previous EnableDebugger bool in context with an object carrying that configuration.

https://github.com/github/c2c-actions/issues/9831

[Copilot]

Pull request overview

This PR adds Dev Tunnels–based remote connectivity for debugger (DAP) jobs by extending the job message contract with tunnel details and updating the worker-side debugger startup to bind to the tunnel-provided port and start a tunnel relay.

Changes:

• Extend AgentJobRequestMessage with DebuggerTunnel payload deserialization (tunnel ID/cluster/token/port) and add the DebuggerTunnelInfo contract type.
• Replace GlobalContext.EnableDebugger with a consolidated DebuggerConfig (enabled + tunnel info) and update debugger enablement checks accordingly.
• Update DapDebugger to require a valid tunnel config, bind to the tunnel port, and start/stop a Dev Tunnel relay; adjust L0 tests to use the new config model.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Test/L0/Worker/DapDebuggerL0.cs	Updates L0 tests to use tunnel-based debugger config and skips relay during unit tests.
src/Test/L0/Sdk/RSWebApi/AgentJobRequestMessageL0.cs	Adds deserialization tests for the new DebuggerTunnel payload.
src/Sdk/DTPipelines/Pipelines/DebuggerTunnelInfo.cs	Introduces the tunnel info DataContract used in job messages.
src/Sdk/DTPipelines/Pipelines/AgentJobRequestMessage.cs	Adds DebuggerTunnel DataMember to the job request message.
src/Runner.Worker/Runner.Worker.csproj	Adds Microsoft.DevTunnels.Connections dependency for relay hosting.
src/Runner.Worker/JobRunner.cs	Switches debugger enablement check to Global.Debugger?.Enabled.
src/Runner.Worker/GlobalContext.cs	Replaces EnableDebugger with DebuggerConfig Debugger.
src/Runner.Worker/ExecutionContext.cs	Populates Global.Debugger from EnableDebugger + DebuggerTunnel in the acquire response.
src/Runner.Worker/Dap/DebuggerConfig.cs	Adds consolidated debugger configuration and tunnel validity check.
src/Runner.Worker/Dap/DapDebugger.cs	Requires valid tunnel config, binds to tunnel port, and starts/stops Dev Tunnel relay.