fix(5595): added logic to use development binary path for uninstall

[kaanyalti]

• Bug

What does this PR do?

Updates how the upgrade command works when used with the --force and --develop flags. Currently if a development agent is already installed, and if a user wants to force install a new development agent, the command uninstalls the production agent, if it exists, and tries to install the development agent again.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

How to test this PR locally

• Install and enroll production agent
• Install and enroll development agent
• Run the development installation command with --force flag and confirm that at the end of the operation both elastic-agent and elastic-development-agent binaries are installed and that both agents are healthy

Related issues

• Closes --force ignores --develop and uninstalls production agent instead #5595

[mergify]

This pull request does not have a backport label. Could you fix it @kaanyalti? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-v8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[michalpristas]

please check integration test failures, these are related

[michalpristas]

this will always fail if err is not nil

[kaanyalti]

I was following similar implementation in the prior test cases, but I can remove the if statement and just assert against the error.

[AndersonQ]

just in case you don't know assert.X will just add a failure to the test, whereas require.X will abort the test. So the idea is to use assert.X for the actual test assertions and require.X during setup to avoid the test continuing after critical failure

[kaanyalti]

I did not know that, thank you

[elastic-sonarqube]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 40%)

See analysis details on SonarQube

[blakerouse]

I don't think this is taking the correct approach currently. I would expect the usage of the following would allow you to get the correct path to the binary that should be called to perform the uninstall.

elastic-agent/internal/pkg/agent/application/paths/common_namespace.go

Line 43 in b6a608d

func InstallNamespace() string {

[blakerouse]

I don't think you can do this, as the --develop is just an alias for the --namespace flag. That allows multiple agents to be installed on the same host at the same time. The name of the executable here should not be hard coded as it should either come from the --namespace flag or from infering the namespace by reading the namespace from the path that is loaded using the full filepath from os.Args[0].