bugfix: Ensure Component Lookup Is Well Formed

This PR introduces an assertion during the component name refinement to
assert that the lookup syntax is well formed. If a developer
accidentally types ":" instead of "::" you will end up with a runtime
erorr that looks like:

```
Uncaught Error: Assertion Failed: fullName must be a proper full name
    at assert (vendor.js:52729)
    at Container.lookup (vendor.js:16581)
    at Class.lookup (vendor.js:43950)
    at layoutFor (vendor.js:28680)
    at lookupComponentPair (vendor.js:28697)
    at lookupComponent (vendor.js:28711)
    at RuntimeResolver._lookupComponentDefinition (vendor.js:28992)
    at RuntimeResolver.lookupComponentHandle (vendor.js:28837)
    at CompileTimeLookup.lookupComponentDefinition (vendor.js:25065)
    at LazyCompiler.resolveLayoutForTag (vendor.js:60366)
```

This message is not actionable for developers. This PR will causes a
compile time error to occur with the following information:

```
Malformed component lookup in "test.js". Got <Foo:Bar \/> but you must use \"::\" to indicate a lookup
```

packages/ember-template-compiler/lib/system/compile-options.ts

@@ -1,4 +1,5 @@
 import { EMBER_STRICT_MODE } from '@ember/canary-features';
+import { assert } from '@ember/debug';
 import { assign } from '@ember/polyfills';
 import { PrecompileOptions } from '@glimmer/compiler';
 import { AST, ASTPlugin, ASTPluginEnvironment, Syntax } from '@glimmer/syntax';
@@ -8,6 +9,10 @@ import COMPONENT_NAME_SIMPLE_DASHERIZE_CACHE from './dasherize-component-name';
 
 let USER_PLUGINS: PluginFunc[] = [];
 
+function malformedComponentLookup(string: string) {
+  return string.indexOf('::') === -1 && string.indexOf(':') > -1;
+}
+
 export default function compileOptions(
   _options: Partial<EmberPrecompileOptions> = {}
 ): PrecompileOptions {
@@ -16,6 +21,11 @@ export default function compileOptions(
     _options,
     {
       customizeComponentName(tagname: string): string {
+        assert(
+          `Malformed component lookup in "${_options.moduleName}". Got <${tagname} /> but you must use "::" to indicate a lookup`,
+          !malformedComponentLookup(tagname)
+        );
+
         return COMPONENT_NAME_SIMPLE_DASHERIZE_CACHE.get(tagname);
       },
     }

packages/ember-template-compiler/tests/system/compile_options_test.js

@@ -15,6 +15,16 @@ moduleFor(
       assert.notEqual(compileOptions(), compileOptions());
     }
 
+    ['@test customizeComponentName asserts name is well formed'](assert) {
+      const options = compileOptions({ moduleName: 'test.js' });
+
+      expectAssertion(() => {
+        options.customizeComponentName('Foo:Bar');
+      }, /Malformed component lookup in "test.js". Got <Foo:Bar \/> but you must use \"::\" to indicate a lookup/);
+
+      assert.ok(options.customizeComponentName('Foo::Bar'));
+    }
+
     ['@test has default AST plugins in resolution mode'](assert) {
       assert.expect(RESOLUTION_MODE_TRANSFORMS.length);