Save git.log.showGraph and git.log.order in state.yml instead of config.yml

[stefanhaller]

showGraph is a setting that can be configured through config.yml, but it can also be toggled at runtime with the <c-l> menu. This dynamically changed value is not saved anywhere though, the next time lazygit starts it reverts back to the value from config.yml.

We should change this so that there's no config setting, only the menu, and its value is saved in state.yml. We did the same change for the diff context size in #2969, and we follow the same pattern for the "ignore whitespace" setting. In general, we should follow this pattern for more things if possible; it makes it easier for people to change settings (editing the config file is cumbersome), and they don't have to quit and restart for the change to take effect.

The same goes for the git.log.order config.

One challenge here is how to migrate people's existing configs. For the diff context size we didn't bother, because it didn't seem like a big deal if people's diff context size reverted back to 3 once; but for showGraph and commit sort order this would be more important, because users could be confused why their graph is no longer showing. This is a bit tricky to do (but not impossible).