GC improvements 7: introduce time_budget GC setting

[teh-cmc]

Adds a configurable time bound to the GC, in addition to the pre-existing space bound.

/// How long the garbage collection in allowed to run for.
///
/// Trades off latency for throughput:
/// - A smaller `time_budget` will clear less data in a shorter amount of time, allowing for a
///   more responsive UI at the cost of more GC overhead and more frequent runs.
/// - A larger `time_budget` will clear more data in a longer amount of time, increasing the
///   chance of UI freeze frames but decreasing GC overhead and running less often.
///
/// The default is an unbounded time budget (i.e. throughput only).
pub time_budget: Duration,

No time budget:

23-11-30_13.22.51.patched.mp4

3.5ms budget:

23-11-30_13.21.27.patched.mp4

---

Part of the GC improvements series:

• GC improvements 0: use-case driven benchmarks #4394
• GC improvements 1: fix timeless tables not being RowId-ordered #4395
• GC improvements 2: VecDeque extensions & benchmarks #4396
• GC improvements 3: turn datastore columns into ring-buffers #4397
• GC improvements 4: index EntityPathHashes in metadata registry #4398
• GC improvements 5: Store{Diff,Event} optimizations #4399
• GC improvements 6: introduce batched GC #4400
• GC improvements 7: introduce time_budget GC setting #4401

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested app.rerun.io (if applicable)
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

• PR Build Summary
• Docs preview
• Examples preview
• Recent benchmark results
• Wasm size tracking

[Wumpf]

makes sense!