Synthetics to push all Heartbeat config options

[paulb-elastic]

This is the Synthetics version of the Kibana UI elastic/kibana#140864 issue, which is about config options that can be done in traditional heartbeat.yml today, that are not supported in the Synthetics UI, or via push.

This issue covers the requirement to add additional config options via push (further to what was initially implemented in #593).

Note that there are other specific issues covering:

• TLS option: Serialize Lightweight Monitor TLS certs  #599
• Multiple hosts: [Project Monitors] Support multiple hosts/urls/ports in lightweight monitors. #627
• (Post 1.0 features) Support proxy_url for browser monitors [Heartbeat] Support proxy_url for browser monitors beats#32162
• ICMP CIDR [ICMP] Add CIDR Notation to Monitors #915

This issue should focus on the other configuration options in Heartbeat

NOTE that the documentation states that ...not all Heartbeat configuration options are supported... which we should update accordingly

[shahzad31]

Also needs to support ssl.renegotiation and

[dominiqueclarke]

response.include_body_max_bytes was also requested by a customer.

[dominiqueclarke]

I don't think this is needed, as synthetics currently already pushes all the configuration it's provided, and Kibana is what tells it if it's supported or not. @paulb-elastic keeping this open for now but can probably close.

[paulb-elastic]

Pushing to post 1.0