Blocks: Add i18n support to register_block_type_from_metadata

Related Gutenberg issue: https://github.com/WordPress/gutenberg/issues/23636.
Related WP-CLI PR: https://github.com/wp-cli/i18n-command/pull/210.
Related documentation proposal: https://github.com/WordPress/gutenberg/blob/master/docs/designers-developers/developers/block-api/block-metadata.md#internationalization-not-implemented

Adds programatic i18n support to `register_block_type_from_metadata` function for block settings registered from `block.json` file that provides `textdomain` field.


Props swissspidy, ocean90.
Fixes #52301.



git-svn-id: https://develop.svn.wordpress.org/trunk@49981 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/blocks/notice/block.asset.php

@@ -0,0 +1,6 @@
+<?php
+
+return array(
+	'dependencies' => array(),
+	'version'      => 'test',
+);

tests/phpunit/data/blocks/notice/block.css

@@ -0,0 +1 @@
+/* Test CSS file */

tests/phpunit/data/blocks/notice/block.js

@@ -0,0 +1 @@
+/* Test JavaScript file. */

tests/phpunit/data/blocks/notice/block.json

@@ -0,0 +1,53 @@
+{
+	"apiVersion": 2,
+	"name": "tests/notice",
+	"title": "Notice",
+	"category": "common",
+	"parent": [
+		"core/group"
+	],
+	"providesContext": {
+		"tests/message": "message"
+	},
+	"usesContext": [
+		"groupId"
+	],
+	"icon": "star",
+	"description": "Shows warning, error or success notices…",
+	"keywords": [
+		"alert",
+		"message"
+	],
+	"textdomain": "notice",
+	"attributes": {
+		"message": {
+			"type": "string",
+			"source": "html",
+			"selector": ".message"
+		}
+	},
+	"supports": {
+		"align": true,
+		"lightBlockWrapper": true
+	},
+	"styles": [
+		{
+			"name": "default",
+			"label": "Default",
+			"isDefault": true
+		},
+		{
+			"name": "other",
+			"label": "Other"
+		}
+	],
+	"example": {
+		"attributes": {
+			"message": "This is a notice!"
+		}
+	},
+	"editorScript": "tests-notice-editor-script",
+	"script": "tests-notice-script",
+	"editorStyle": "tests-notice-editor-style",
+	"style": "tests-notice-style"
+}

tests/phpunit/data/languages/plugins/notice-pl_PL.po

@@ -0,0 +1,43 @@
+msgid ""
+msgstr ""
+"Project-Id-Version: \n"
+"POT-Creation-Date: 2015-12-31 16:31+0100\n"
+"PO-Revision-Date: 2021-01-14 18:26+0100\n"
+"Language: pl_PL\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"X-Generator: Poedit 2.4.2\n"
+"X-Poedit-Basepath: .\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+"X-Poedit-KeywordsList: __;_e;_x:1,2c;_ex:1,2c;_n:1,2;_nx:1,2,4c;_n_noop:1,2;"
+"_nx_noop:1,2,3c;esc_attr__;esc_html__;esc_attr_e;esc_html_e;esc_attr_x:1,2c;"
+"esc_html_x:1,2c\n"
+"X-Textdomain-Support: yes\n"
+"Last-Translator: \n"
+"Language-Team: \n"
+"X-Poedit-SearchPath-0: .\n"
+
+msgctxt "block title"
+msgid "Notice"
+msgstr "Powiadomienie"
+
+msgctxt "block description"
+msgid "Shows warning, error or success notices…"
+msgstr "Wyświetla ostrzeżenie, błąd lub powiadomienie o sukcesie…"
+
+msgctxt "block keyword"
+msgid "alert"
+msgstr "ostrzeżenie"
+
+msgctxt "block keyword"
+msgid "message"
+msgstr "wiadomość"
+
+msgctxt "block style label"
+msgid "Default"
+msgstr "Domyślny"
+
+msgctxt "block style label"
+msgid "Other"
+msgstr "Inny"