Edit license script for Java, add manual licenses for xz

[emilymye]

• Move from using a privately-managed git repo file to a local file for xz-java
• Update java license script for to providing absolute file path

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ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---			---	---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[emilymye]

R: @ibzib @tvalentyn

[emilymye]

I'm not sure what's up with the RAT precommit (seems to make sense, but also not sure I can get around it?)

[emilymye]

Run Java PreCommit

[tvalentyn]

would it help to rename COPYING to LICENSE? Also, I can't see the Rat error in the log or on the jenkins worker

[emilymye]

I added both manual license folders to exemptions since we don't want to add the license header to license files.