Mark a couple of constructors as explicit and use the default
constructor instead of defining an empty body for PreParserSourceRange.

Bug: v8:9396
Change-Id: I60f891245543852d8250105ba7b89620c15204bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1706052
Auto-Submit: Dan Elphick <delphick@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62766}