Upgrade to HtmUnit 3.11.0

This commit upgrades to a major new release of HtmlUnit. This is a
breaking change as HtmlUnit 3 moves to a `org.htmlunit` package and
calling code needs to be restructured.

Our use of Selenium has been adapted accordingly, moving to Selenium
3, using the new org.seleniumhq.selenium:htmlunit3-driver integration.

Closes gh-30392

framework-docs/modules/ROOT/pages/testing/spring-mvc-test-framework/server-htmlunit/mah.adoc

@@ -8,8 +8,7 @@ to use the raw HtmlUnit libraries.
 == MockMvc and HtmlUnit Setup
 
 First, make sure that you have included a test dependency on
-`net.sourceforge.htmlunit:htmlunit`. In order to use HtmlUnit with Apache HttpComponents
-4.5+, you need to use HtmlUnit 2.18 or higher.
+`org.htmlunit:htmlunit`.
 
 We can easily create an HtmlUnit `WebClient` that integrates with MockMvc by using the
 `MockMvcWebClientBuilder`, as follows:

framework-docs/modules/ROOT/pages/testing/spring-mvc-test-framework/server-htmlunit/webdriver.adoc

@@ -166,7 +166,7 @@ following sections to make this pattern much easier to implement.
 == MockMvc and WebDriver Setup
 
 To use Selenium WebDriver with the Spring MVC Test framework, make sure that your project
-includes a test dependency on `org.seleniumhq.selenium:selenium-htmlunit-driver`.
+includes a test dependency on `org.seleniumhq.selenium:selenium-htmlunit3-driver`.
 
 We can easily create a Selenium WebDriver that integrates with MockMvc by using the
 `MockMvcHtmlUnitDriverBuilder` as the following example shows:

framework-docs/modules/ROOT/pages/testing/spring-mvc-test-framework/server-htmlunit/why.adoc

@@ -87,7 +87,7 @@ Kotlin::
 
 This test has some obvious drawbacks. If we update our controller to use the parameter
 `message` instead of `text`, our form test continues to pass, even though the HTML form
-is out of synch with the controller. To resolve this we can combine our two tests, as
+is out of sync with the controller. To resolve this we can combine our two tests, as
 follows:
 
 [tabs]