Refactor application structure and initialize core components

I decided to rewrite the program taking into account the experience gained.

internal/ffmpeg/utilities.go

@@ -0,0 +1,48 @@
+package ffmpeg
+
+import (
+	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/internal/application/setting"
+)
+
+type UtilitiesContract interface {
+	GetFFmpeg() FFmpegContract
+	GetFFprobe() FFprobeContract
+	GetFFplay() FFplayContract
+}
+
+type utilities struct {
+	setting setting.SettingContract
+	ffmpeg  FFmpegContract
+	ffprobe FFprobeContract
+	ffplay  FFplayContract
+}
+
+func NewUtilities(setting setting.SettingContract) UtilitiesContract {
+	return &utilities{
+		setting: setting,
+	}
+}
+
+func (u *utilities) GetFFmpeg() FFmpegContract {
+	if u.ffmpeg == nil {
+		u.ffmpeg = newFFmpeg(u.setting.GetFFmpegPath())
+	}
+
+	return u.ffmpeg
+}
+
+func (u *utilities) GetFFprobe() FFprobeContract {
+	if u.ffprobe != nil {
+		u.ffprobe = newFFprobe(u.setting.GetFFprobePath())
+	}
+
+	return u.ffprobe
+}
+
+func (u *utilities) GetFFplay() FFplayContract {
+	if u.ffplay == nil {
+		u.ffplay = newFFplay(u.setting.GetFFplayPath())
+	}
+
+	return u.ffplay
+}