gpui: Add per-window frame-duration and present-interval histograms (#61871)

GPUI's input-latency histograms only sample frames that were preceded by
input, so a window that janks while animating or while streaming content
(agent panel output, terminal scrollback) never shows up in the fleet's
latency reports. Hang detection catches outright stalls, but frames that
are merely late — stutters in the 30–100ms range during animation —
currently aren't visible anywhere.

This adds a `frame-duration-histogram` feature to GPUI with a per-window
tracker recording two histograms: the duration of every `Window::draw`,
and the interval between consecutively presented frames while the window
is animating (a next-frame callback was already scheduled at the
previous present, so frames are being produced back-to-back and a
stretched interval means frames were missed). Intervals are only
recorded for active windows, since inactive windows are deliberately
throttled to a lower frame rate, and re-presents of unchanged frames
(e.g. sustaining the display's refresh rate during high-rate input) are
excluded. Zed enables the feature and reports both histograms every five
minutes as a "Frame Duration Report" telemetry event alongside the
existing "Latency Report", bucketed at roughly the 120Hz/60Hz/30Hz frame
budgets so dropped-frame rates can be aggregated across the fleet.


Release Notes:

- Added frame rendering performance to the diagnostics Zed collects when
telemetry is enabled, to help find and fix stutters and dropped frames.