Prevent new rows from mistakenly removing existing rows in internals UI

Prior to this change, the following situation could occur:

1. Pending reports with ID 123 and 456 are added to the UI table.
2. Report with ID 123 is sent, invoking the updateRows method, which
   sees that ID 456 is not in the list of updated rows and therefore
   removes it.

This change avoids calling updateRows when a single row is being added
and instead finds the existing row with the same ID, if any.

Bug: 340585314
Change-Id: Id0bcd8a3d9112dc08b40320bd71e8fede783e33c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5544979
Reviewed-by: Nan Lin <linnan@chromium.org>
Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1302037}