Add -v/--version flag to print version string (#3883)

* Add `-v/--version` flag to print version string

- Created a new flag `-v/--version` in the command-line interface to display the version number and exit.
- Moved all version-related functions inside the config package to the new file `manager/config/version.go` to avoid circular dependencies.
- Added a new `GetVersionString()` function to generate a formatted version string.
- Updated references to the moved version functions.
- Updated references in the `Makefile`.

* Move version embeds to build package

* Remove githash var

---------

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

internal/manager/config/init.go

@@ -11,6 +11,7 @@ import (
 	"github.com/spf13/pflag"
 	"github.com/spf13/viper"
 
+	"github.com/stashapp/stash/internal/build"
 	"github.com/stashapp/stash/pkg/fsutil"
 	"github.com/stashapp/stash/pkg/logger"
 )
@@ -25,6 +26,7 @@ type flagStruct struct {
 	cpuProfilePath string
 	nobrowser      bool
 	helpFlag       bool
+	versionFlag    bool
 }
 
 func GetInstance() *Instance {
@@ -47,6 +49,11 @@ func Initialize() (*Instance, error) {
 			os.Exit(0)
 		}
 
+		if flags.versionFlag {
+			fmt.Printf(build.VersionString() + "\n")
+			os.Exit(0)
+		}
+
 		overrides := makeOverrideConfig()
 
 		_ = GetInstance()
@@ -134,6 +141,7 @@ func initFlags() flagStruct {
 	pflag.StringVar(&flags.cpuProfilePath, "cpuprofile", "", "write cpu profile to file")
 	pflag.BoolVar(&flags.nobrowser, "nobrowser", false, "Don't open a browser window after launch")
 	pflag.BoolVarP(&flags.helpFlag, "help", "h", false, "show this help text and exit")
+	pflag.BoolVarP(&flags.versionFlag, "version", "v", false, "show version number and exit")
 
 	pflag.Parse()