Made context_propagation_only dynamic

[JonasKunz]

• May the instrumentation collect sensitive information, such as secrets or PII (ex. in headers)?
  • [ ] Yes
  • [ ] Add a section to the spec how agents should apply sanitization (such as sanitize_field_names)
  • [x] No
  • [ ] Why?
  • [ ] n/a
• [x] Create PR as draft
• [x] Approval by at least one other agent
• [x] Mark as Ready for Review (automatically requests reviews from all agents and PM via CODEOWNERS)
  • Remove PM from reviewers if impact on product is negligible
  • Remove agents from reviewers if the change is not relevant for them
• [x] Approved by at least 2 agents + PM (if relevant)
• [x] Merge after 7 days passed without objections \ To auto-merge the PR, add /schedule YYYY-MM-DD to the PR description.
• [x] Create implementation issues through the meta issue template (this will automate issue creation for individual agents)
• [x] If this spec adds a new dynamic config option, add it to central config.

[trentm]

trentm approved these changes on behalf of https://github.com/orgs/elastic/teams/apm-agent-python and https://github.com/orgs/elastic/teams/apm-agent-node-js

Hrm. That is an slightly unexpected side-effect of being on the apm-agent-python team to do the odd PR review for Colton. :)