## Summary

Closes elastic#162045

This PR adds an API integration test for the following scenario:
- Given an integration with some non secret (plain text) vars that
become secret in a newer version;
- When Fleet has an agent policy with this integration and upgrades from
the old to the newer version;
- Then the vars that have become secrets should correctly be stored as
secret values.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

---------

Co-authored-by: Julia Bardi <90178898+juliaElastic@users.noreply.github.com>
(cherry picked from commit 766ff8f)

…64666)

# Backport

This will backport the following commits from `main` to `8.10`:
- [[Fleet] Add secrets package API integration test
(#164583)](#164583)

<!--- Backport version: 8.9.7 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Jill
Guyonnet","email":"jill.guyonnet@elastic.co"},"sourceCommit":{"committedDate":"2023-08-24T07:37:34Z","message":"[Fleet]
Add secrets package API integration test (#164583)\n\n##
Summary\r\n\r\nCloses
https://github.com/elastic/kibana/issues/162045\r\n\r\nThis PR adds an
API integration test for the following scenario:\r\n- Given an
integration with some non secret (plain text) vars that\r\nbecome secret
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integration and upgrades from\r\nthe old to the newer version;\r\n- Then
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Add secrets package API integration test (#164583)\n\n##
Summary\r\n\r\nCloses
https://github.com/elastic/kibana/issues/162045\r\n\r\nThis PR adds an
API integration test for the following scenario:\r\n- Given an
integration with some non secret (plain text) vars that\r\nbecome secret
in a newer version;\r\n- When Fleet has an agent policy with this
integration and upgrades from\r\nthe old to the newer version;\r\n- Then
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Add secrets package API integration test (#164583)\n\n##
Summary\r\n\r\nCloses
https://github.com/elastic/kibana/issues/162045\r\n\r\nThis PR adds an
API integration test for the following scenario:\r\n- Given an
integration with some non secret (plain text) vars that\r\nbecome secret
in a newer version;\r\n- When Fleet has an agent policy with this
integration and upgrades from\r\nthe old to the newer version;\r\n- Then
the vars that have become secrets should correctly be stored
as\r\nsecret values.\r\n\r\n### Checklist\r\n\r\n- [x] [Unit or
functional\r\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\r\nwere
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BACKPORT-->

Co-authored-by: Jill Guyonnet <jill.guyonnet@elastic.co>

* main: (3152 commits)
  [Security Solution][Detection Engine] fixes 410 error on index legacy template call (#164682)
  [SavedObjects] Create serverless roots for jest integration tests (#164157)
  Create upselling package and implement EntityAnalytics serverless upselling (#164136)
  [Fleet] Change 'Out-of-date' to 'Outdated policy' in agent list table (#164673)
  [IndexManagement] Use internal base path for API (#164665)
  [Profiling] removing ~ symbol (#164595)
  [Telemetry] Fetch snapshot: allow specifying the version via querystring (#164670)
  [Cases] Show warning when all cases table reaches 10k cases message (#164323)
  [ML] Removing token list from text expansion model testing (#164560)
  [Fleet] Add secrets package API integration test (#164583)
  [Fleet] Fix security solution tag id (#164582)
  [Security Solution] Modal says "duplicating 0 rules" when you duplicate an individual rule (#163908)
  [api-docs] 2023-08-24 Daily api_docs build (#164658)
  [APM] Cleanup alerting api tests (#164438)
  Upgrade EUI to 87.2.0 (#164385)
  [ML] Fix query bar autocompletion for ML and AIOps embeddables (#164485)
  [Fleet] Fix flaky unit test for the details page (#164641)
  [Security Solution] update codeowner for serverless security subdir (#164640)
  [Security Solution] Fixes Assistant Connector and Actions RBAC Flow (#164382)
  [Discover] Removing large string truncation from doc viewer (#164236)
  ...