SSR support for complex template expressions (#5511)

* feat: added ability to toggle experimentalComplexExpressions in ssr fixtures

* chore: disable

* feat: ssr cte support

* fix: ssr coverage

* chore: revert test change

* fix: additional testing around ssr specific codepaths

* fix: additional testing around ssr specific codepaths

Author: jhefferman-sfdc

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/config.json

@@ -0,0 +1,8 @@
+{
+    "entry": "x/attribute-dynamic-complex",
+    "experimentalComplexExpressions": true,
+    "ssrFiles": {
+        "expected": "expected-ssr.html",
+        "error": "error-ssr.txt"
+    }
+}

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/error-ssr.txt

@@ -0,0 +1 @@
+LWC1034: Ambiguous attribute value class="{bar() + foo()}". If you want to make it a valid identifier you should remove the surrounding quotes class={bar() + foo()}. If you want to make it a string you should escape it class="\{bar() + foo()}".

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/error.txt

@@ -0,0 +1,6 @@
+<fixture-test>
+  <template shadowrootmode="open">
+    <div class="foobar">
+    </div>
+  </template>
+</fixture-test>

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/expected-ssr.html

@@ -0,0 +1,3 @@
+<template>
+    <div class="{bar() + foo()}"></div>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/expected.html

@@ -0,0 +1,10 @@
+import { LightningElement } from 'lwc';
+
+export default class AttributeDynamicComplex extends LightningElement {
+    bar() {
+        return 'foo';
+    }
+    foo() {
+        return 'bar';
+    }
+}

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/modules/x/attribute-dynamic-complex/attribute-dynamic-complex.html

@@ -0,0 +1,8 @@
+{
+    "entry": "x/for-each-block",
+    "experimentalComplexExpressions": true,
+    "ssrFiles": {
+        "expected": "expected-ssr.html",
+        "error": "error-ssr.txt"
+    }
+}

packages/@lwc/engine-server/src/__tests__/fixtures/attribute-dynamic-complex/modules/x/attribute-dynamic-complex/attribute-dynamic-complex.js

@@ -0,0 +1 @@
+LWC1034: Ambiguous attribute value for:each="{list()}". If you want to make it a valid identifier you should remove the surrounding quotes for:each={list()}. If you want to make it a string you should escape it for:each="\{list()}".