parser: change 'level' in parse api back to string

We changed to operate on an int internally in I92daeb0f7be8a0.
Let's cast it back to a string for the api in order to prevent
a breaking change, which is not really necessary.

Bug: T304171
Change-Id: I5f5a9203b4dd085cb5defba72c6650532bc9e8d1

includes/parser/Parser.php

@@ -4407,7 +4407,8 @@ class Parser {
 			}
 			$tocraw[] = [
 				'toclevel' => $toclevel,
-				'level' => $level,
+				// cast $level to string in order to keep b/c for the parse api
+				'level' => (string)$level,
 				'line' => $tocline,
 				'number' => $numbering,
 				'index' => ( $isTemplate ? 'T-' : '' ) . $sectionIndex,

tests/phpunit/includes/parser/ParserMethodsTest.php

@@ -127,7 +127,7 @@ class ParserMethodsTest extends MediaWikiLangTestCase {
 		$this->assertSame( [
 			[
 				'toclevel' => 1,
-				'level' => 2,
+				'level' => '2',
 				'line' => 'foo',
 				'number' => '1',
 				'index' => '1',
@@ -137,7 +137,7 @@ class ParserMethodsTest extends MediaWikiLangTestCase {
 			],
 			[
 				'toclevel' => 1,
-				'level' => 2,
+				'level' => '2',
 				'line' => 'bar',
 				'number' => '2',
 				'index' => '',
@@ -147,7 +147,7 @@ class ParserMethodsTest extends MediaWikiLangTestCase {
 			],
 			[
 				'toclevel' => 1,
-				'level' => 2,
+				'level' => '2',
 				'line' => 'baz',
 				'number' => '3',
 				'index' => '2',