fix(parser): propagate multi-level break/continue before trailing statements of enclosing bodies

[AlessioGiacobbe]

Problem

break N / continue N are lowered to a countdown flag plus a plain break, but the propagation check was emitted only at the end of each enclosing loop body — so statements between the inner construct and the end of the body still executed:

foreach ([1, 2, 3] as $x) {
    foreach ([1, 2, 3] as $y) {
        break 2;
    }
    echo "leaked\n";   // printed by the compiled binary, not by PHP
}

On the native (int-typed) switch path the check also sat inside the do { switch ... } while(0) wrapper, decrementing the flag a second time for the switch level the C++ break had already exited — so break 2 from a native switch inside a loop never exited the loop at all.

Fix

• Emit the propagation check immediately after every nested loop/switch statement (from parseStmts) and drop the now-dead end-of-body emissions, including the double-decrementing one in the native-switch wrapper.
• When the check sits directly inside a switch (new FunctionContext::$breakableIsSwitch), a continue landing on that level lowers to break, matching PHP's continue-targets-switch semantics.
• parseBreak/parseContinue validate the level against the number of enclosing breakable constructs (new FunctionContext::$breakableDepth), reproducing PHP's compile-time error (Cannot 'break' 2 levels). The countdown scheme relies on this to always reach zero at an enclosing construct.

Tests

• New break-continue-level-placement.phpt: 8 scenarios with observable side effects (break/continue 2 and 3 across loops, both switch lowerings, continue targeting a switch). Expected output generated by running the same code under PHP 8.4.
• The continue-2-while scenario in break-continue-level.phpt encoded the old behavior: its trailing $i++ only ran because of the misplaced check, and standard PHP loops forever on that code (verified). The counter now advances before the inner loop.
• control_flow + loop + switch suites: 38/40 pass; the 2 foreach-iterator-* failures are deprecation-notice noise that fails identically on master. No new PHPStan errors. A compiled 5-scenario repro diffs clean against PHP 8.4 output.