Refactor templated event and link generation

[stoewer]

This PR makes the initialization phase and generation phase of events and links more similar to the initialization and generation of resources and spans.

Additionally the PR makes the following changes:

• Event times now have a random offset
• Attributes for random events and links now take the cardinality parameter into account
• The template.js example creates a diverse range of events, exceptions and links
• Update to the latest Go and golangci-lint version

[zalegrala]

Looks reasonable to me.