Simplify the RebaseMode enum

- Remove REBASE_MODE_NORMAL. It is not the "normal" mode anyway, rather a legacy
mode; we have removed support for it in eb0f7e3d02, so there's no point in
representing it in the enum.
- Remove distinction between REBASE_MODE_REBASING and REBASE_MODE_INTERACTIVE;
these are the same now.
- Rename StatusCommands.IsInInteractiveRebase to IsInRebase.
- Remove StatusCommands.RebaseMode; use StatusCommands.IsInRebase instead.

pkg/commands/git_commands/commit_loader_test.go

@@ -487,7 +487,7 @@ func TestCommitLoader_getConflictedCommitImpl(t *testing.T) {
 			builder := &CommitLoader{
 				Common:              common,
 				cmd:                 oscommands.NewDummyCmdObjBuilder(oscommands.NewFakeRunner(t)),
-				getWorkingTreeState: func() enums.RebaseMode { return enums.REBASE_MODE_INTERACTIVE },
+				getWorkingTreeState: func() enums.RebaseMode { return enums.REBASE_MODE_REBASING },
 				dotGitDir:           ".git",
 				readFile: func(filename string) ([]byte, error) {
 					return []byte(""), nil