[graf] Move the current libjpg builtin to the latest version and the builtin directory

[dpiparo]

This PR does two things:

1. Adds in the builtins directory libjpeg in its latest released version, 3.1.3, as sources, to stick to the current way of doing in ROOT. The way in which sources are pruned, e.g. of tests, is clearly described.
2. Removes the old builtin, buried in graf2d/asimage/src/libAfterImage/libjpeg and adapts CMake to take advantage of the newly located builtin.

This was possible only thanks to the assistance and CMake experience of @hageboeck , whom I thank.

@couet @guitargeek @bellenot FYI

[github-actions]

Test Results

    20 files      20 suites   2d 18h 6m 40s ⏱️
 3 809 tests  3 808 ✅ 1 💤 0 ❌
68 789 runs  68 780 ✅ 9 💤 0 ❌

Results for commit 063157a.

♻️ This comment has been updated with latest results.