Reland "[Messaging] Exclude self and owner from member added/removed messages"

This is a reland of commit eec2fcb8542c4f4b2606e1daf7093715367763d4
There was uinitialized value for the role field struct GroupMember.
Fixing that should fix the Msan bot failures in crbug.com/393057112.

Original change's description:
> [Messaging] Exclude self and owner from member added/removed messages
>
> This CL excludes self and owner from member addition / removal
> messages. This exclusion applies to storage in DB, instant messages,
> and activity log.
>
> Bug: 392968190
> Change-Id: I2bd167ed4c29db5755fda990e2f9d957ea15f0ee
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6210781
> Reviewed-by: Yuheng Huang <yuhengh@chromium.org>
> Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1412767}

Bug: 392968190, 393057112
Change-Id: I7de2a7ce448d8a0823845f3107840d131853d2fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6213790
Auto-Submit: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: Yuheng Huang <yuhengh@chromium.org>
Commit-Queue: Yuheng Huang <yuhengh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1413034}