Expose ES tag keys directly in the OTEL config file

[pavolloffay]

Created from #2295 (comment)

Add tag keys directly in the OTEL config file instead of a separate tag key file.

      --es.tags-as-fields.config-file string                  (experimental) Optional path to a file containing tag keys which will be stored as object fields. Each key should be on a separate line.

[joe-elliott]

@pavolloffay I'd like to work on this feature.

This is marked area/otel, but I assume this would require changes in the elastic search options, opentelemetry translator and the traditional jaeger es spanstore.

[pavolloffay]

The Config/Options objects will have to be adjusted. The translator and spanstore shouldn't require any changes since they should already get parsed keys.

[joe-elliott]

Ok, that's what I was seeing. Just wanted to make sure this wasn't an otel change only for some reason.

[joe-elliott]

@pavolloffay this was fixed in #2417 and can be closed. I mentioned the wrong # in the PR. Apologies for the mixup.

[pavolloffay]

Done in #2417