Respect metered connections in Agent Host, CLI, and browser telemetry

[dmitrivMS]

Context

#336922 contains the desktop core/debugger telemetry fixes from #331685 for #297362, now split into a dedicated PR stacked on the native metered service in #331897. The additional collectors below were explicitly deferred from that consolidation and need separate metered-connection support.

Remaining paths

When telemetry is otherwise enabled, these paths do not currently receive metered-connection state:

• Agent Host telemetry: agentHostTelemetryService.ts constructs its own 1DS collector, and agentHostMicrosoftTelemetry.ts creates separate internal collectors.
• CLI telemetry: cliProcessMain.ts constructs a collector and telemetry service without a metered service.
• Browser-local telemetry: the web appender makes an unconditional endpoint-health request. The browser telemetry service filters events when the telemetry integration is applied, but does not pause its physical collector or health probe.

Expected follow-up

• Respect network.meteredConnection for these collectors, including initial-state readiness where applicable.
• Suppress health probes, scheduled/retry sends, and shutdown sends while metered, and resume correctly when unmetered.
• Preserve existing telemetry consent, telemetry-level restrictions, and enterprise policy behavior.
• Add deterministic transport-level tests; do not send real telemetry during validation.

This is a follow-up for these specific VS Code-owned collectors, not a request to add completion-provider behavior or broadly change extension/provider-owned telemetry.