Update to Java 11

[datho7561]

• Bump to 0.30.0-SNPASHOT, since updating to Java 11 breaks API
• Use --release 11 in maven compiler plugin
• Use Java 11 in the Jenkinsfiles
• Update tycho to 2.7.5 (the newest version that supports Java 11)
• Update to the latest lsp4j, adapt to the API changes, and remove the guava exclusion (lsp4j no longer ships with guava, so we don't need to exclude it)
• Delete ToStringBuilder and use the one from lsp4j
• Update to the newest jetty version that supports Java 11

[rgrunber]

Nice. And this will set us up to finally address #1291 (Fred has a draft PR for it) .

[datho7561]

I added the necessary reflection config to ensure the server launches. I poked around a bit with a few features and it seems to be working, with no exceptions in the logs.

[angelozerr]

LGTM.

I suggest that we merge the PR ASAP in order to see some potential problem when we will develop xml features.

[rgrunber]

Hold on. I see a few one reference to 1.8 related stuff. Would be good to verify whether this should remain or change :

lemminx/org.eclipse.lemminx/src/main/java/org/eclipse/lemminx/utils/ToStringBuilder.java

Lines 29 to 30 in e507183

	* @implNote This class originally came from xbase.lib and has been extended for LSP4J purposes with some additional functionality.
	* It then was copied due to java 1.8 compatibility requirements into lemminx.

[datho7561]

@rgrunber I deleted that file and used the one from lsp4j; I'll double check the binary still works first though

update yep it still works

[datho7561]

Another line about 1.8:
https://github.com/eclipse-lemminx/lemminx/blob/main/org.eclipse.lemminx/pom.xml#L294

I'll update jetty as well I guess

update: I've updated jetty to the newest version that supports Java 11. Jetty is used in the test suite.