Java 3738 download and attach agent

[BrianPhillips2020]

In this PR

• Adds InstallAgentTask which downloads the agent if one is not supplied and can attach the agent to specified tasks (in this case hardcoded to Test tasks) via java args.
• Adds ContrastConfigurationExtension
• Update READMEs
• Add EndToEndTests which require gradle properties to run to avoid accidentally hammering TS with requests for new agents

TODO (tickets linked if exist)

• Figure out specifics for how the agent should be attached to running tests. Auto attach when tests run? Configured to attach to supplied tasks? Require property to attach or to not attach? JAVA-8882
• Manual testing shows the agent does not start when attached to tests due to failing to retrieve ServerSettings from TS, investigate and fix
• Provide configuration option for allowing extra Contrast Configurations JAVA-8887
• Configure Proxy for SDK JAVA-8883
• Implement real logging, requires redesigning one test JAVA-8885

[BrianPhillips2020]

Manual testing shows the agent does not start when attached to tests due to failing to retrieve ServerSettings from TS, investigate and fix

I still don't know why this is happening yet. I think it's because my test was running with /api at the end of the url I was providing to my ts instance, and server settings is just trying to reach the normal serverSettings endpoint but with /api in the middle of it and getting confused. I'm gonna try to fix

[BrianPhillips2020]

Manual testing shows the agent does not start when attached to tests due to failing to retrieve ServerSettings from TS, investigate and fix

I still don't know why this is happening yet. I think it's because my test was running with /api at the end of the url I was providing to my ts instance, and server settings is just trying to reach the normal serverSettings endpoint but with /api in the middle of it and getting confused. I'm gonna try to fix

This was it, lol. The agent was using the same configurations I provided to the SDK, which hits similar endpoints but requires that /api appended to the urls.