Fix crash/freeze when zooming out too far in a plot (#5737)

### What
We reach `i64::MAX` pretty quickly when zooming out on e.g.
https://github.com/rerun-io/example-rs-github-stars.

In debug builds this overflow would lead to a crash. In release I think
it results in a freeze.

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* [x] I've included a screenshot or gif (if applicable)
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* Using newly built examples:
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[app.rerun.io](https://app.rerun.io/pr/5737/index.html?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[app.rerun.io](https://app.rerun.io/pr/5737/index.html?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
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- [PR Build Summary](https://build.rerun.io/pr/5737)
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- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
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Author: emilk

crates/re_space_view_time_series/src/space_view_class.rs

@@ -400,15 +400,15 @@ It can greatly improve performance (and readability) in such situations as it pr
             .x_axis_formatter(move |time, _, _| {
                 format_time(
                     time_type,
-                    time.value as i64 + time_offset,
+                    (time.value as i64).saturating_add(time_offset),
                     time_zone_for_timestamps,
                 )
             })
             .y_axis_width(3) // in digits
             .label_formatter(move |name, value| {
                 let name = if name.is_empty() { "y" } else { name };
                 let label = time_type.format(
-                    (value.x as i64 + time_offset).into(),
+                    ((value.x as i64).saturating_add(time_offset)).into(),
                     time_zone_for_timestamps,
                 );
 
@@ -803,7 +803,12 @@ fn ns_grid_spacer(
 
     let mut small_spacing_ns = 1;
     while width_ns / (next_grid_tick_magnitude_ns(small_spacing_ns) as f64) > max_medium_lines {
-        small_spacing_ns = next_grid_tick_magnitude_ns(small_spacing_ns);
+        let next_ns = next_grid_tick_magnitude_ns(small_spacing_ns);
+        if small_spacing_ns < next_ns {
+            small_spacing_ns = next_ns;
+        } else {
+            break; // we've reached the max
+        }
     }
     let medium_spacing_ns = next_grid_tick_magnitude_ns(small_spacing_ns);
     let big_spacing_ns = next_grid_tick_magnitude_ns(medium_spacing_ns);
@@ -828,7 +833,11 @@ fn ns_grid_spacer(
             step_size: step_size as f64,
         });
 
-        current_ns += small_spacing_ns;
+        if let Some(new_ns) = current_ns.checked_add(small_spacing_ns) {
+            current_ns = new_ns;
+        } else {
+            break;
+        };
     }
 
     marks