[deprecation] Deprecate JsonThrowOnErrorRector as it can cause BC breaks

[TomasVotruba]

Deprecates JsonThrowOnErrorRector, following the same pattern as #8324.

The rule adds JSON_THROW_ON_ERROR to every json_encode() / json_decode() call:

-json_encode($content);
-json_decode($json);
+json_encode($content, JSON_THROW_ON_ERROR);
+json_decode($json, null, 512, JSON_THROW_ON_ERROR);

This is a BC break, not a cleanup. Before the change a malformed payload returns false or null; after it, the same payload throws JsonException. Code that relied on the silent return value now fatals at runtime:

// before: $data is null, the if-branch handles it
// after: JsonException is thrown, the if-branch is never reached
$data = json_decode($json);
if ($data === null) {
    return $this->fallback();
}

Every call site has to be reviewed by hand to decide whether an exception is wanted and where it gets caught. Rector cannot make that call, so the rule is deprecated instead. For consistent error reporting on any PHP version, a wrapper tool like nette/utils Json::decode() is the better fit.

The rule was in no set, so no user config is silently affected.

Changes:

• JsonThrowOnErrorRector implements DeprecatedInterface, refactor() throws ShouldNotHappenException
• removed its test + fixtures
• removed tests/Issues/ScopeNotAvailable/JsonThrowCaseSensitiveConstFetchTest.php, a regression test that only existed to cover this rule