[MU3 Backend] ENG-68: Fix pedal endpoints on other tracks

[iveshenry18]

Resolves: ENG-68: Pedals anchored to staff 1 or voice 2 terminate incorrectly

Sometimes pedals are imported that begin or end on segments that have
notes on tracks (or staves) other than the track the spanner is on.
Previously, this would cause incorrect tick adjustments on "change"
type pedals, and it would result in some pedals not being able to
compute a start or end element. This commit fixes these issues by
considering all tracks of a part when assessing pedal change tick
adjustments and when computing start elements.

• I signed CLA
• I made sure the code in the PR follows the coding rules
• I made sure the code compiles on my machine
• I made sure there are no unnecessary changes in the code
• I made sure the title of the PR reflects the core meaning of the issue you are solving
• I made sure the commit message(s) contain a description and answer the question "Why do those changes fix that particular issue?" or "Why are those changes really necessary as improvements?"
• I made sure the commit message title starts with "fix #424242:" if there is a related issue
• I created the test (mtest, vtest, script test) to verify the changes I made

[iveshenry18]

Changes added to #8766