[iOS] Handle an integer type in ConvertedResultFromScriptResult()

When https://crrev.com/c/2590748 removed the CRWJSInjection* classes
from DOMDistiller, it also updated the ValueResultFromScriptResult()
method to ConvertedResultFromScriptResult() using the base::Value
class. However, in handling number types, the CL made the following
change:

  `result_type == CFNumberGetTypeID()` -> `value->is_double()`

The original condition was true for both integers and doubles,
but the new condition only holds true for doubles. As a result,
an assertion could occur if the value is an integer.

This CL resolves the issue by adding the integer type handling.

Bug: 361711113
Change-Id: I79214dcee74fba2460c4e7ad719af6d597e1f083
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5803890
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Éric Noyau <noyau@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/main@{#1346674}