Fix checks web tests for current plugin API

The plugin web tests now compile against the plugin npm dependency set
from Gerrit. That exposes @types/sinon and the current
@gerritcodereview/typescript-api package.

Drop the hand-written global sinon variable declaration from the test
setup. @types/sinon already provides the ambient sinon namespace, and
tests that use the runtime object should import it explicitly. Add
imports in the two tests that still relied on the bare global.

Update the Gerrit styles mock from icon to material to match the plugin
API package used by the build.

Trim the create-new-checker button text before comparing it. Chromium
now preserves the template whitespace around the label in innerText.

Change-Id: I9e4d1f8a27c5b3061e8f9ad24b7c515e0d382f16

web/gr-checkers-list_test.ts

diff --git a/web/gr-checkers-list_test.ts b/web/gr-checkers-list_test.ts
index 36efa9a..f9ca93e 100644
--- a/web/gr-checkers-list_test.ts
+++ b/web/gr-checkers-list_test.ts
@@ -21,6 +21,7 @@
 import {queryAll, queryAndAssert} from './test/test-util';
 import {PluginApi} from '@gerritcodereview/typescript-api/plugin';
 import {assert} from '@open-wc/testing';
+import sinon from 'sinon';
 
 const CHECKERS = [
   {
@@ -190,7 +191,7 @@
   test('create new checker button renders corrrectly', () => {
     const div = queryAndAssert<HTMLElement>(element, '#createNewContainer');
     const button = queryAndAssert<HTMLElement>(div, 'gr-button');
-    assert.equal(button.innerText, 'Create New');
+    assert.equal(button.innerText.trim(), 'Create New');
   });
 
   test('table of checkers renders correctly', async () => {

web/gr-repo-chip_test.ts

diff --git a/web/gr-repo-chip_test.ts b/web/gr-repo-chip_test.ts
index 2e1f406..e438e72 100644
--- a/web/gr-repo-chip_test.ts
+++ b/web/gr-repo-chip_test.ts
@@ -19,6 +19,7 @@
 import {queryAndAssert} from './test/test-util';
 import {GrRepoChip} from './gr-repo-chip';
 import {fixture, html, assert} from '@open-wc/testing';
+import sinon from 'sinon';
 
 suite('gr-repo-chip tests', () => {
   let element: GrRepoChip;

web/test/test-setup.ts

diff --git a/web/test/test-setup.ts b/web/test/test-setup.ts
index 4f113a1..b335daa 100644
--- a/web/test/test-setup.ts
+++ b/web/test/test-setup.ts
@@ -22,7 +22,6 @@
   interface Window {
     sinon: typeof sinon;
   }
-  let sinon: typeof sinon;
 }
 window.sinon = sinon;
 
@@ -31,7 +30,7 @@
   styles: {
     font: css``,
     form: css``,
-    icon: css``,
+    material: css``,
     menuPage: css``,
     spinner: css``,
     subPage: css``,