[APM] Documentation links using ElasticDocsLink.tsx don't always work

[bmorelli25]

The ElasticDocsLink.tsx component uses the version of Kibana to generate links to documentation.

kibana/x-pack/legacy/plugins/apm/public/components/shared/Links/ElasticDocsLink.tsx

Lines 19 to 23 in 472e7fb

	export function ElasticDocsLink({ section, path, ...rest }: Props) {
	const { version } = useApmPluginContext().packageInfo;
	const href = `https://www.elastic.co/guide/en${section}/${version}${path}`;
	return <EuiLink href={href} {...rest} />;
	}

This is fine, except when running a version of Kibana like 8.0.0, or 7.6.0-snapshot. Documentation for those versions don't exist, which breaks the links that use the component.

As an example, when running 7.6.0-snapshot: "How to add labels and other data" links to
https://www.elastic.co/guide/en/apm/get-started/7.6.0-SNAPSHOT/metadata.html instead of
https://www.elastic.co/guide/en/apm/get-started/7.6/metadata.html.

kibana/x-pack/legacy/plugins/apm/public/components/shared/MetadataTable/index.tsx

Lines 57 to 61 in 472e7fb

	<ElasticDocsLink section="/apm/get-started" path="/metadata.html">
	<EuiText size="s">
	<EuiIcon type="help" /> How to add labels and other data
	</EuiText>
	</ElasticDocsLink>

Is it possible for this component to use the {config.docs.version} that the links in the APM tutorial use? This method uses the correct documentation version for external links`. As an example:

kibana/x-pack/plugins/apm/server/tutorial/index.ts

Line 84 in 472e7fb

'{config.docs.base_url}guide/en/apm/get-started/{config.docs.version}/index.html',

[elasticmachine]

Pinging @elastic/apm-ui (Team:apm)