tracing-collector: raise field truncation limit

Summary:
32 was way too low for seeing longer names. I don't see why we can't just make it nice and big.

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Differential Revision: D105911128

fbshipit-source-id: 7b86ca34afb9f31391f35c85347801036f43003d

Author: muirdm

eden/scm/lib/tracing-collector/src/model.rs

@@ -1018,8 +1018,8 @@ impl<'a> DescribeTreeSpan<TreeSpanExtra> for TracingTreeDescriptor<'a> {
             .map(|item| {
                 let k = strings.get(*item.0);
                 let v = strings.get(*item.1);
-                let v = if v.len() > 32 {
-                    format!("{}...", &v[..30])
+                let v = if v.len() > 256 {
+                    format!("{}...", &v[..253])
                 } else {
                     v.to_string()
                 };