tabular_data_preview: Revive filter funnel icon (#63266)

# Objective

Originally, `IconName::Filter` was a funnel glyph and
`IconName::Sliders` was used for settings/controls.

In #60937 (commit `1a06fd4f2b`), `filter.svg` was replaced with the
sliders glyph, and `sliders.svg` / `Sliders` enum variants were deleted.
Consequently, `IconName::Filter` has become a sliders-shaped icon used
across 8+ surfaces in Zed (git_ui, search, debugger_ui, keymap_editor,
language_tools, quick_action_bar, editor view settings).

When moving tabular data preview settings to follow the editor's
convention (using `IconName::Filter` sliders for table view settings),
column filter buttons in the table header were left using the same
sliders icon instead of a traditional funnel.

Repurposing `IconName::Filter` back to a funnel would break all other UI
surfaces across Zed.

## Solution

- Restored the funnel icon under a new dedicated
`IconName::FilterFunnel` variant (`assets/icons/filter_funnel.svg` and
`crates/icons/src/icons.rs`).
- Updated `tabular_data_preview` column filter trigger buttons
(`table_header.rs`) to use `IconName::FilterFunnel`.
- Left all existing `IconName::Filter` (sliders) usages across the app
untouched.

Before:
<img width="363" height="156" alt="image"
src="https://github.com/user-attachments/assets/84ac5f87-c0f7-4de9-94ea-e4040e3b4a4a"
/>

After:
<img width="361" height="151" alt="image"
src="https://github.com/user-attachments/assets/38514f3a-0710-4273-b227-4623bf78410b"
/>

## Testing

- `cargo check -p icons -p tabular_data_preview` and `./script/clippy`
build clean.
- `cargo test -p tabular_data_preview --lib` passes.
- Verified column filter button renders the funnel icon in tabular data
preview and highlights correctly when filters are active.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Replace column filter icon in tabular data preview with filter funnel

assets/icons/filter_funnel.svg

@@ -0,0 +1,3 @@
+<svg width="16" height="16" viewBox="0 0 16 16" fill="none" xmlns="http://www.w3.org/2000/svg">
+<path d="M12.9416 2.99643C13.08 2.79636 12.9568 2.5 12.7352 2.5H3.26475C3.04317 2.5 2.91999 2.79636 3.0584 2.99643L6.04033 7.30646C6.24713 7.60535 6.35981 7.97674 6.35981 8.3596C6.35981 9.18422 6.35981 11.4639 6.35981 12.891C6.35981 13.2285 6.59643 13.5 6.88831 13.5H9.11168C9.40357 13.5 9.64019 13.2285 9.64019 12.891C9.64019 11.4639 9.64019 9.18422 9.64019 8.3596C9.64019 7.97674 9.75289 7.60535 9.95969 7.30646L12.9416 2.99643Z" stroke="#DCE0E5" stroke-width="1.2" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>