This CL refactors the torque-compiler module slightly to allow
compilation of string inputs in addition to file path inputs. The
added functionality is then used to implement the first
'goto type defintion' unit test.

R=tebbi@chromium.org

Bug: v8:8880
Change-Id: I178a387abda6e319e66d41c50431cb139ac6e9f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1503263
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60047}