Add some JVM metrics

[erikfinnman]

Feature Description
The component currently only emits system metrics like memory usage. It would be more valuable to have some metrics for the JVM as well, like heap usage and garbage collection statistics.

Use Case
Monitoring the health of the Greengrass runtime would be easier.

Proposed Solution
See e.g. what SpringBoot provides as runtime information:
https://docs.spring.io/spring-boot/docs/2.1.13.RELEASE/reference/html/production-ready-metrics.html#production-ready-metrics-meter