Child of MDL-80971.

Need to make sure the following commits, which touch mod_lti, are also made in the feature branch. Some of this code has been copied to core_ltix (no git move) so rebase won't catch all of these:

Hash: 24f59be234cf8534538b7b7c4e35cfce31c913b4
  https://github.com/moodle/moodle/commit/24f59be234cf8534538b7b7c4e35cfce31c913b4
  https://tracker.moodle.org/browse/MDL-82344
Hash: 29a541724f5b8f8820ace881ef4387b8ebec9be0
  https://github.com/moodle/moodle/commit/29a541724f5b8f8820ace881ef4387b8ebec9be0
  https://tracker.moodle.org/browse/MDL-65292
Hash: a180dba31403b481f9899407a5052022f96ed32a
  https://github.com/moodle/moodle/commit/a180dba31403b481f9899407a5052022f96ed32a
  https://tracker.moodle.org/browse/MDL-81549
Hash: e6f75b59a30634dd48b8b07da71a1d7aa67d1fe3
  https://github.com/moodle/moodle/commit/e6f75b59a30634dd48b8b07da71a1d7aa67d1fe3
  https://tracker.moodle.org/browse/MDL-80248
Hash: 777d00ef37e8588a2ba74cea302e9553c2f0e85d
  https://github.com/moodle/moodle/commit/777d00ef37e8588a2ba74cea302e9553c2f0e85d
  https://tracker.moodle.org/browse/MDL-82344
Hash: 1f76843f25eccc56bf7be844d9254ad54a4b4b4e
  https://github.com/moodle/moodle/commit/1f76843f25eccc56bf7be844d9254ad54a4b4b4e
  https://tracker.moodle.org/browse/MDL-81337
Hash: dab4a2b66f079330365e90ad93175468758eb6f3
  https://github.com/moodle/moodle/commit/dab4a2b66f079330365e90ad93175468758eb6f3
  https://tracker.moodle.org/browse/MDL-80079
Hash: 10f8e19f40ec641d95f0587ce653799bb4134c8b
  https://github.com/moodle/moodle/commit/10f8e19f40ec641d95f0587ce653799bb4134c8b
  https://tracker.moodle.org/browse/MDL-78284