Make "gn analyze" know about all inputs for jinja_template()

* Renames compute_grit_inputs_for_analyze -> compute_inputs_for_analyze
* Computes .py inputs via exec_script (when compute_inputs_for_analyze=true)
* Enforce that sub-included .jinja files are listed in targets.

Bug: 843562
Change-Id: I3698c7846375530a86474bd5960bb002ac45f71a
Reviewed-on: https://chromium-review.googlesource.com/1112867
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570650}
7 files changed