[PHP] Autovivification should produce warning on union type if not guarded with IF-STATEMENT

### Description

This issue is related to #5070.
#5070 is only applied on simple value.

If a statement enconter:
- a function/method with nullable or array union return type,
- or a function/method with nullable or array union argument type,
- or object property with nullable or array union type.

there should be a warning message to prevent error, but this warning can be supressed by IF-STATEMENT. The IF condition must contains ```is_null``` or ```is_array``` as a guard.

### Use case/motivation

```php
prop1;
$var2 = $inst->prop2;
$var3 = $inst->prop3;
$var4 = $inst->prop4;

$var1[] = 100; // this statement should display warning, var1 could be int
$var2[] = 100; // this statement should display warning, var2 could be int or float
$var3[] = 100; // this statement should display warning, var3 could be string
$var4[] = 100; // this statement must display error, var4 is not array nor null

if (is_null($var1)) {
$var1[] = 100; // OK, var1 is guarded
$var2[] = 100; // this statement should display warning, var2 is not guarded
$var3[] = 100; // this statement should display warning, var3 is not guarded
$var4[] = 100; // this statement must display error, var4 is not array nor null
}

if (is_array($var1)) {
// this statement should display warning, var1 is never reach here.
// i.e. warning message is not related with autovivification.
$var1[] = 100;
}

if (is_null($var4)) {
// this statement should display warning, var4 is never reach here.
// i.e. warning message is not related with autovivification.
$var4[] = 100;
}

// -------------------------------------------------------------------------------------

function func1(): ?int {}
function func2(): int|float|null {}
function func3(): string|array {}
function func4(): string|bool {}

$var5 = func1();
$var6 = func2();
$var7 = func3();
$var8 = func4();

// do the same as object properties

// -------------------------------------------------------------------------------------

$myClosure = function() use ($var1, $var2, $var4, $var4) {
// do the same as object properties
}

// -------------------------------------------------------------------------------------

function func1 (
?int $arg1,
int|float|null $arg2,
string|array $arg3,
string|bool $arg4,
) {
// do the same as object properties
}

```

### Related issues

_No response_

### Are you willing to submit a pull request?

No

### Code of Conduct

Yes

No source files or tests are named; start by reviewing related issue #5070 and reproducing the PHP examples in the issue. Done means union-typed autovivification produces warnings unless guarded by is_null or is_array, while invalid non-array cases still produce errors.

Written by the indexing model from the issue text.