telemetry: add more latency fields to invokeLLM metric

[chungjac]

Problem

• invokeLLM metric needs more fields for latency

Solution

• amazonq_invokeLLM metric has these fields:
  • latency
  • toolCallLatency
  • timeToFirstChunk
  • timeBetweenChunks

Note

• I would've liked to use a more reusable/general name such as latency2 (like how we have requestId and requestId2) instead of toolCallLatency which seems very specific to only tools. However, I have already put in the implementation PR to make the deadline for the flare release, as flare release happens 1 day before toolkit release.
• VSC is the only IDE which requires a version bump for aws-toolkit-common. All other IDEs (JB, Eclipse, VS) use flare as the source of truth for metrics.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.