refactor: reduce telemetry events count

[ZanSara]

Proposed Changes:

• remove Haystack imported telemetry event
• make pipelines send one event only for the first run call after the pipeline config has changed meaningfully
• consolidate LLM events to reduce their impact

How did you test it?

• CI

Notes for the reviewer

n/a

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added tests that demonstrate the correct behavior of the change
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[vblagoje]

@ZanSara Just saw this PR and remembered that we might still be sending events for each PromptTemplate loaded. We should prevent components from sending events automatically on load - if so desired.

[ZanSara]

@vblagoje that part should be gone in telemetry v2. We're now sending events only on very limited situations. This telemetry should not be to assess absolute usage numbers, just relative ones: which docstore is more popular, which nodes are never used, etc. It doesn't try to understand how many people use the various components, just whether they're used at all.