Make token as a default authentication provider instead of basic

[azasypkin]

Recently we introduced token authentication provider (relies on Token Management APIs provided by Elasticsearch) that can and should be used instead of basic authentication provider. But to make that happen we should take care of the following things first:

• Figure out if xpack.security.authc.token.enabled can be set in Elasticsearch distribution by default in 8.0.0 (cc @elastic/es-security)
• Switch majority of our functional tests to work with token authentication provider (Switch functional tests to use token authentication provider instead of basic #34337).
• Add support for long-lived tokens to support Reporting, Alerting etc (API Key Management #25729).
• Merge basic token with token provider types to easily fall back to the old behaviour if tokens cannot be used for any reason

Blocked by: #61115

[elasticmachine]

Pinging @elastic/kibana-security

[jkakavas]

Figure out if xpack.security.authc.token.enabled can be set in Elasticsearch distribution by default

The setting used to default to false and now defaults to the value of xpack.security.http.ssl.enabled. The reason is that we do not want to enable the token service over an unencrypted layer (http) as this would mean that

• clients would send user credentials over http ( password grant in the Get Token API)
• clients would send access tokens over http ( Authorization header )
• clients would send refresh tokens over http ( refresh_token grant

We'd need to see if it is worth relaxing this stance, if TLS for the http layer can't be enabled by default.

[azasypkin]

Thanks @jkakavas! Let's see how we can move this forward. I guess same thing is true for xpack.security.authc.api_key.enabled (aka long-lived tokens).