Jar installation issues and conflicts such as snakeyaml-engine

[jsvd]

Logstash's use of JRuby's jar dependencies will currently cause troubles given:
a) jars aren't being correctly installed due to an issue in modern ruby-maven/ruby-maven-libs
b) a new psych was released, creating a clash between the 2.7 version of snakeyaml-engine shiiped in jruby and the one being fetched by translate filter (newest, currently 2.9).

Errors can look like:

no such file to load -- org/snakeyaml/snakeyaml-engine/2.9/snakeyaml-engine-2.9.jar
Did you mean?  org/snakeyaml/snakeyaml-engine/2.7/snakeyaml-engine-2.7 (LoadError). Bundler cannot continue.
 #  from /usr/share/logstash/logstash-core-plugin-api/logstash-core-plugin-api.gemspec:24
 #  -------------------------------------------
 #  
 >  require "logstash-core-plugin-api/version"
 #  
 #  -------------------------------------------
org.jruby.exceptions.StandardError: (GemspecError) 
[!] There was an error while loading `logstash-core-plugin-api.gemspec`: 
    you might need to reinstall the gem which depends on the missing jar or in case there is Jars.lock then resolve the jars with `lock_jars` command
no such file to load -- org/snakeyaml/snakeyaml-engine/2.9/snakeyaml-engine-2.9.jar
Did you mean?  org/snakeyaml/snakeyaml-engine/2.7/snakeyaml-engine-2.7 (LoadError). Bundler cannot continue.

A Draft PR aims to temporarily address both issues: #16919