Refactor: Introduce declarative configuration layer

[Aki-7]

Preparation for #71 #39 .

Enable to load configurations like this.

@Configuration
public class Config {
    @ConfigOption(env = "OTEL_EXPORTER_OTLP_ENDPOINT", required = true)
    public String endpoint;

    @ConfigOption(env = "SOME_ENV")
    public Pattern value = Pattern.compile("^default value$");
}

Config conf = new Config();
ConfigParser parser = new ConfigParser(conf);
parser.parse();

It supports loading config from environment variables using a env attribute.
And I'm planning to add more attributes if needed to load configurations from files, system properties, etc...

Checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your master branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• All follow-ups are documented as issues and-or TODO comments
• Ensure you have provided tests - that demonstrates feature works or fixes the issue
• Please update user documentation if needed
• Please update developer documentation if needed

[stellargo]

Looks great overall :) Still trying out the plugin to leave any comments from functional perspective, but leaving few minor comments

[stellargo]

hey, you can define ".*" as a common constant

[oleg-nenashev]

It is possible, but overall it is an overkill when there is just one usage

[stellargo]

similarly, can define this string in common constants as well

[oleg-nenashev]

same. OTOH there is a typo

Suggested change

	LOGGER.log(Level.WARNING, "Failed to road configuration", e);
	LOGGER.log(Level.WARNING, "Failed to load configuration", e);

[stellargo]

instead of asserting for boolean hasError you can do:
@Test(expected = ConfigurationParseException.class)

[stellargo]

linting

[oleg-nenashev]

There is a typo that needs to be fixed. Also I would suggest adding documentation in the same pull request.

P.S: This framework might also be an overkill and may create issues if we ever try to package Jenkins agents as native images. It is not a problem in foreseeable future

[oleg-nenashev]

It is not the best practice in general, because it would catch 'Error's that should be fatal. In this case it leads to a failure