[breaking] Pass user locale preference directly to i18n package (#1365)

The user can configure their locale preference via the `locale` configuration key. This information is given priority by
the `github.com/arduino/arduino-cli/configuration` package over the automatically detected locale.

Previously, the `i18n` package got the configuration setting from the `github.com/arduino/arduino-cli/configuration`
package, but this will result in an import cycle when the `i18n` package is used to enable translation of the output
strings of the `configuration` package.

To avoid this, the caller now reads the configuration and passes the locale code to the `i18n` package via its `Init`
function:

i18n.Init("it")

The argument can be omitted if only automated locale detection is needed:

i18n.Init()

Author: per1234

Diff for: docs/UPGRADING.md

@@ -6,6 +6,21 @@ Here you can find a list of migration guides to handle breaking changes between
 
 ### Change public library interface
 
+#### `github.com/arduino/arduino-cli/i18n` package
+
+The behavior of the `Init` function has changed. The user specified locale code is no longer read from the
+`github.com/arduino/arduino-cli/configuration` package and now must be passed directly to `Init` as a string:
+
+```go
+i18n.Init("it")
+```
+
+Omit the argument for automated locale detection:
+
+```go
+i18n.Init()
+```
+
 #### `github.com/arduino/arduino-cli/arduino/builder` package
 
 `GenBuildPath()` function has been moved to `github.com/arduino/arduino-cli/arduino/sketch` package. The signature is

Diff for: i18n/i18n.go

@@ -15,18 +15,20 @@
 
 package i18n
 
-import "github.com/arduino/arduino-cli/configuration"
-
 // Init initializes the i18n module, setting the locale according to this order of preference:
-// 1. Configuration set in arduino-cli.yaml
+// 1. Locale specified via the function call
 // 2. OS Locale
 // 3. en (default)
-func Init() {
+func Init(configLocale ...string) {
 	initRiceBox()
 	locales := supportedLocales()
 
-	if configLocale := configuration.Settings.GetString("locale"); configLocale != "" {
-		if locale := findMatchingLocale(configLocale, locales); locale != "" {
+	if len(configLocale) > 1 {
+		panic("Multiple arguments not supported")
+	}
+
+	if len(configLocale) > 0 && configLocale[0] != "" {
+		if locale := findMatchingLocale(configLocale[0], locales); locale != "" {
 			setLocale(locale)
 			return
 		}

Diff for: main.go

@@ -26,7 +26,7 @@ import (
 
 func main() {
 	configuration.Settings = configuration.Init(configuration.FindConfigFileInArgsOrWorkingDirectory(os.Args))
-	i18n.Init()
+	i18n.Init(configuration.Settings.GetString("locale"))
 	arduinoCmd := cli.NewCommand()
 	if err := arduinoCmd.Execute(); err != nil {
 		os.Exit(errorcodes.ErrGeneric)