test: failed capture-expression evaluation is reported, not dropped

Add tests/ext/live-debugger/debugger_capture_expression_error.phpt: a
log probe with a capture expression that cannot evaluate (getmember on
an int) now produces an evaluationErrors entry instead of no output.

Author: p-ddsign

tests/ext/live-debugger/debugger_capture_expression_error.phpt

@@ -0,0 +1,66 @@
+--TEST--
+A failed capture-expression evaluation is reported, not silently dropped
+--SKIPIF--
+<?php include __DIR__ . '/../includes/skipif_no_dev_env.inc'; ?>
+--ENV--
+DD_AGENT_HOST=request-replayer
+DD_TRACE_AGENT_PORT=80
+DD_TRACE_GENERATE_ROOT_SPAN=0
+DD_DYNAMIC_INSTRUMENTATION_ENABLED=1
+DD_REMOTE_CONFIG_POLL_INTERVAL_SECONDS=0.1
+--INI--
+datadog.trace.agent_test_session_token=live-debugger/capture_expression_error
+--FILE--
+<?php
+
+require __DIR__ . "/live_debugger.inc";
+
+reset_request_replayer();
+
+class Bar {
+    function foo($arg1) {
+        return $arg1;
+    }
+}
+
+await_probe_installation(function() {
+    build_log_probe([
+        "where" => ["typeName" => "Bar", "methodName" => "foo"],
+        "segments" => [["str" => "log"]],
+        "captureExpressions" => [
+            // getmember on an int cannot evaluate -> per-expression error
+            ["name" => "bad", "expr" => ["json" => ["getmember" => [["ref" => "arg1"], "nope"]]]],
+        ],
+    ]);
+
+    \DDTrace\start_span(); // submit span data
+});
+
+(new Bar)->foo(10);
+
+$dlr = new DebuggerLogReplayer;
+$errors = null;
+for ($i = 0; $i < 3 && $errors === null; $i++) {
+    $log = json_decode($dlr->waitForDebuggerDataAndReplay()["body"], true)[0];
+    if (isset($log["debugger"]["snapshot"]["evaluationErrors"])) {
+        $errors = $log["debugger"]["snapshot"]["evaluationErrors"];
+    }
+}
+var_dump($errors);
+
+?>
+--CLEAN--
+<?php
+require __DIR__ . "/live_debugger.inc";
+reset_request_replayer();
+?>
+--EXPECTF--
+array(1) {
+  [0]=>
+  array(2) {
+    ["expr"]=>
+    string(%d) "%s"
+    ["message"]=>
+    string(%d) "%s"
+  }
+}