[META 672] Add option for when to capture the Elasticsearch query

[elastic-apm-tech]

See meta issue and spec for the description and details:

• Meta issue: https://github.com/elastic/apm/issues/672
• Spec issue: https://github.com/elastic/apm/issues/673

[basepi]

Should just be a change to the default behavior, since we don't plan to add the new config value to the python agent.

[felixbarny]

This is what the spec says:

Agents MAY offer this configuration option. If they don't, they MUST use a hard-coded list of URLs that correspond with the default value of this option.

So it's fine if you don't want to expose a config option, but the default behavior must be aligned (with the exact same wildcard matchers). At that point, exposing the config option is probably also not more work.