fix: correctly reset tempo on frame change when retrieve channel state setting is used

[henrikvilhelmberglund]

This pull request aims to correctly reset the tempo on frame change when the retrieve channel state setting is used.
Eg. right now if you have a groove Oxx or Fxx in only the first pattern and change the frame while playing back, the tempo is reset using the default speed/tempo instead of the retrieved groove/speed settings. This PR changes this to correctly reset the tempo to the actual groove setting used so the tempo stays consistent even when changing frames during playback.

It looks like there was some groove/speed handling in there already (which didn't work using retrieve channel state) so I split that code with an if/else depending on General.bRetrieveChanState and took the working code from CSoundGen::ApplyGlobalState(). Maybe there's a smarter way to fix this, if that's the case feel free to edit.

fixes #357

Changes in this PR:

• (cite all changes made in the PR for change log)
  • Correctly reset tempo on frame change when retrieve channel state setting is used (fixes Pressing up/down in focused frame list makes playback ignore inherited Fxx commands #357)

[Gumball2415]

i cannot edit PRs with branches from external repositories, so i'll have to recreate this PR in a new branch, if desired

[henrikvilhelmberglund]

Do you know why? I have Allow edits by maintainers checked

But yes you can make a new PR if that's better.

[Gumball2415]

oh, i guess i was wrong. i recall trying this on a different PR of yours and it didn't work