Add package settings and icon

[jalvz]

Motivation/summary

This makes host and secret_token configurable, primarily for the Docker use case.

While at it, it also adds the APM icon

Checklist

• I have signed the Contributor License Agreement.
• I have updated CHANGELOG.asciidoc

I have considered changes for:

• documentation
• logging (add log lines, choose appropriate log selector, etc.)
• metrics and monitoring (create issue for Kibana team to add metrics to visualizations, e.g. Kibana#44001)
• automated tests (add tests for the code changes, all unit tests pass locally)
• telemetry
• Elasticsearch Service (https://cloud.elastic.co)
• Elastic Cloud Enterprise (https://www.elastic.co/products/ece)
• Elastic Cloud on Kubernetes (https://www.elastic.co/elastic-cloud-kubernetes)

How to test these changes

Related issues

Closes #4540

Partially implements #4495

Screenshots

[apmmachine]

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Build stats

• Build Cause: Branch indexing

• Start Time: 2020-12-16T02:50:15.129+0000

• Duration: 47 min 11 sec

Test stats 🧪

Test	Results
Failed	0
Passed	4613
Skipped	124
Total	4737

Steps errors

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Run Window tests

• Took 9 min 14 sec . View more details on here

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• Description: tar --exclude=coverage-files.tgz -czf coverage-files.tgz coverage

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• Description: tar --exclude=system-tests-linux-files.tgz -czf system-tests-linux-files.tgz system-tests

Test Sync

• Took 3 min 15 sec . View more details on here
• Description: ./.ci/scripts/sync.sh

[simitt]

nit: this is not only for Docker, also when it should be reachable outside of localhost.

[codecov-io]

Codecov Report

Merging #4542 (20461e9) into master (736812b) will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4542      +/-   ##
==========================================
- Coverage   75.98%   75.89%   -0.10%     
==========================================
  Files         161      161              
  Lines        9789     9789              
==========================================
- Hits         7438     7429       -9     
- Misses       2351     2360       +9     

Impacted Files	Coverage Δ
publish/acker.go	78.94% <0.00%> (-10.53%)	⬇️
kibana/connecting_client.go	61.40% <0.00%> (-8.78%)	⬇️
processor/otel/consumer.go	93.51% <0.00%> (-0.45%)	⬇️

[axw]

Tested with 7.11 BC1, using apm-integration-testing with a small patch to make --with-elastic-agent work with --bc: elastic/apm-integration-testing#1011. I manually configured kibana (through config/kibana.yml) to use the snapshot registry:

xpack.fleet.registryUrl: 'https://epr-staging.elastic.co'

The integration shows up with the icon:

host and secret_token show up in the settings, but secret_token is incorrectly defined to be a bool: