Revert "LinkPreview: Add alt+hover and long press triggers"

This reverts commit bbb01fbd.

Reason for revert: issue 327651304 top Canary crasher

Original change's description:
> LinkPreview: Add alt+hover and long press triggers
>
> This CL adds alt+hover and long press triggers, and a feature param
> "trigger_type" for LinkPreview to control available trigger type.
>
> Before this CL, Link Preview used only Alt+click trigger. Now it is
> controlled by features::LinkPreviewTriggerType::kAltClick.
>
> For this purpose, this CL introduces
>
> - WebLinkPreviewTriggerer: receives signals and determine to trigger
>   Link Preview.
> - WebLinkPreviewInitiator: mediates initiation request to blink side.
>
> Fixed: b:314233999, 1522049
> Change-Id: Ic3f2bc4108ce514156086c473a9727d7a10c27d0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5107229


> Reviewed-by: Alex Ilin <alexilin@chromium.org>
> Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
> Reviewed-by: Kent Tamura <tkent@chromium.org>
> Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
> Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
> Commit-Queue: Ken Okada <kenoss@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1266909}

Change-Id: I2bf4e1ab0315bf327da2dc9f914fe18d5af5ba23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5334966
Owners-Override: Prudhvikumar Bommana <pbommana@google.com>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Prudhvikumar Bommana <pbommana@google.com>
Cr-Commit-Position: refs/heads/main@{#1267369}