Time filter shows a (rounded) suffix and custom preset labels

## Summary

Three changes to the new time filter (date range picker). Custom presets defined in the timepicker:quickRanges advanced setting now show their configured display label, such as Financial Year to Date, instead of the raw bounds, and recent ranges that match a preset reuse that name. When a relative bound carries a rounding suffix, for example now-1y/y typed by you or produced by the Round relative time ranges setting, the time filter button and the Presets list append a (rounded) suffix, so Last 1 year for -1y and Last 1 year (rounded) for -1y/y. Whole calendar buckets such as Today or Yesterday do not get the suffix. The PR also fixes a regression where the legacy dateFormat advanced setting leaked into the displayed range: that setting now only affects how typed absolute dates are parsed, and the display always uses the picker's own format.

**Why this needs docs:** The Filtering page documents the Round relative time ranges setting and the Presets list at a level where the new (rounded) indicator is a visible omission, and the preset-label fix confirms behavior the page already implies.

## Resources

- PR [#289066](https://github.com/elastic/kibana/pull/289066) — [DateRangePicker] "rounded" suffix, custom preset labels, input date formats

Screenshots from PR


## Availability

| Channel | Details |
|---------|---------|
| **Stack** | v9.5.4, v9.6.0 |
| **Serverless** | Sep 7–Sep 11 |
| **Feature status** | preview |
| **Feature flag** | None — active by default |

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*Created with [Docs Quest Scanner](https://github.com/florent-leborgne/docs-quest-scanner) by @florent-leborgne*

## Suggested edits

[Filtering in Kibana](https://www.elastic.co/docs/explore-analyze/query-filter/filtering) > Time filter (stack: preview 9.5+, serverless: preview applies-item)
- **What the docs say:** Open gear Settings to configure automatic refresh and time display: ... Turn Round relative time ranges on or off.
- **What to add:** Add one sentence to the Round relative time ranges bullet, or to the Presets bullet, stating that when a relative range is rounded the time filter and the Presets list show a (rounded) suffix after the label, for example Last 1 year (rounded) for -1y/y. Mention that whole-day ranges such as Today and Yesterday do not get the suffix. Use an inline {applies_to} tag at the start of the new paragraph or list item because the surrounding applies-item covers 9.5+. Applies from 9.6.0 and in serverless (technical preview). A 9.5.4 backport is targeted, verify the shipped patch before using it as the floor.

[Filtering in Kibana](https://www.elastic.co/docs/explore-analyze/query-filter/filtering) > Time filter, accepted formats table
- **What the docs say:** Preset labels | Last 24 hours or any other range listed under Presets.
- **What to add:** Optional: clarify that custom presets configured by an administrator in the timepicker:quickRanges advanced setting appear under Presets with their configured display name, and that you can enter that name as text. This confirms behavior the row already implies and closes the gap where the label previously showed as raw bounds. Keep it to one sentence, no version tag needed because the intended behavior did not change. Applies from 9.6.0 and in serverless (technical preview).