Upgrades to:
* Xtext 2.23.0
* Xtend 2.23.0
* LSP 0.9.0
For Xtext release notes see: https://www.eclipse.org/Xtext/releasenotes.html#/releasenotes/2020/09/01/version-2-23-0
The Xtext dependencies are now managed using their BOM which makes it easier to keep them in sync.
Because Xtext depends on a newer ASM version some runtime dependencies were also upgraded:
* ASM 8.0.1
* Pax Web 7.2.15
* XBean 4.17.0
Signed-off-by: Wouter Born <github@maindrain.net>
