Restructure embedded web server packages

[philwebb]

[philwebb]

See also #8303

[garyrussell]

Is there a doco issue to reflect this change (didn't see one from a quick search). For example here references EmbeddedServletContainerInitializedEvent when it's now ServletWebServerInitializedEvent.

[wilkinsona]

Thanks for spotting this, @garyrussell. There isn't a separate documentation issue as far as I know so I've reopened this one.

[philwebb]

Thanks. I forgot about the documentation.

[snicoll]

@philwebb I can see a bunch of existing classes that were moved got their @since tag changed to 2.0.0. Do you really meant to do that? I understand it is a new location but it makes extermely difficult for someone to know when a feature was introduced. For instance, we advertize @LocalServerPort is a 2.0 feature now. It isn't...

[philwebb]

@snicoll We should discuss this on the next call I guess. It was intentional, my thinking being that if someone is referring to a specific class in a third party library they should know when it was introduced. The concept of @LocalServerPort may have existed before 2.0 but the org.springframework.boot.web.server.LocalServerPort class did not.