Clean POM file

[nyg]

Here are the changes I did:

• Used sortpom to sort the elements within the POM file. Apache actually recommends a specific order for POM elements, see here.
• Updated scm and issueManagement URLs, replaced jiaqi by LeMyst.
• Removed a duplicated guava dependency. I checked by running mvn dependency:tree | grep guava and only the correct version is returned.
• Created properties for each dependency versions.
• Removed the parent POM. As it belongs to jiaqi and he's probably not going to update it anymore, I think it's better to remove it. Java version is now Java 17 instead of Java 8.

What I also recommend is that you:

• Change the value of <groupId> (e.g. to something like org.LeMyst) so you can remove -lemyst suffix in version number.
• Remove ciManagement if it's not used anymore.

[LeMyst]

Hi @nyg
Thanks for your PR,
Sorry for the time this take.
I think it will be good this time.

[nyg]

@LeMyst no problem :) I updated my PR once more, let me know if there's anything else I should do.