proxy: add more columns to parquet upload (#6405)

## Problem

Some fields were missed in the initial spec.

## Summary of changes

Adds a success boolean (defaults to false unless specifically marked as
successful).
Adds a duration_us integer that tracks how many microseconds were taken
from session start through to request completion.

proxy/src/proxy.rs

@@ -356,6 +356,7 @@ pub async fn proxy_pass(
     compute: impl AsyncRead + AsyncWrite + Unpin,
     aux: MetricsAuxInfo,
 ) -> anyhow::Result<()> {
+    ctx.set_success();
     ctx.log();
 
     let usage = USAGE_METRICS.register(Ids {