[8.16](backport #6273) Log warning on same version upgrade to prevent failed status

[mergify]

What does this PR do?

Log warning on same version upgrade and filter error to prevent upgrade status reporting.
If a user attempts to upgrade to the same version, the elastic-agent upgrade call will exit with an error, but the agent's status will be cleared of any upgrade markers.

Include an earlier check for same-version upgrades before artifacts are downloaded to prevent unnecessary downloads

Why is it important?

Currently upgrading to the same version results in the agent reporting a failed state until a successful upgrade can be done.

Testing instructions

Install a stand-alone agent and use elastic-agent upgrade 9.0.0-SNAPSHOT --source-uri file://path/to/dir --skip-verification to upgrade the agent

For example:

# Install the agent
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo ./elastic-agent install --develop
Installing into development namespace; this is an experimental and currently unsupported feature.
Elastic Agent will be installed at /Library/Elastic/Agent-Development and will run as a service. Do you want to continue? [Y/n]:y
Do you want to enroll this Agent into Fleet? [Y/n]:n
[   =] Service Started  [4s] Elastic Agent successfully installed, starting enrollment.
[   =] Done  [4s]
Elastic Agent has been successfully installed.

# Check status and version
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo elastic-development-agent version
Binary: 9.0.0-SNAPSHOT (build: 14e78753e6c06295e3348a00de01ae54905fb2c0 at 2024-12-18 18:30:32 +0000 UTC)
Daemon: 9.0.0-SNAPSHOT (build: 14e78753e6c06295e3348a00de01ae54905fb2c0 at 2024-12-18 18:30:32 +0000 UTC)
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo elastic-development-agent status
┌─ fleet
│  └─ status: (STOPPED) Not enrolled into Fleet
└─ elastic-agent
   └─ status: (HEALTHY) Running

# attempt to upgrade to the same version
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo elastic-development-agent upgrade 9.0.0-SNAPSHOT --source-uri file:///Users/mlaterman/git/elastic-agent/build/distributions/ --skip-verify
Upgrade triggered to version 9.0.0-SNAPSHOT, Elastic Agent is currently restarting
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ echo $?
0
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo elastic-development-agent status
┌─ fleet
│  └─ status: (STOPPED) Not enrolled into Fleet
└─ elastic-agent
   └─ status: (HEALTHY) Running
elastic-agent-9.0.0-SNAPSHOT-darwin-aarch64|⇒ sudo elastic-development-agent version
Binary: 9.0.0-SNAPSHOT (build: 14e78753e6c06295e3348a00de01ae54905fb2c0 at 2024-12-18 18:30:32 +0000 UTC)
Daemon: 9.0.0-SNAPSHOT (build: 14e78753e6c06295e3348a00de01ae54905fb2c0 at 2024-12-18 18:30:32 +0000 UTC)

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

Disruptive User Impact

N/A

Related issues

• Closes 8.13.0+ Fleet managed agents upgraded to the currently running version report failed upgrades until a successful upgrade occurs #6186

  ---

  This is an automatic backport of pull request Log warning on same version upgrade to prevent failed status #6273 done by Mergify.

[michel-laterman]

buildkite test this

[mergify]

This pull request has not been merged yet. Could you please review and merge it @michel-laterman? 🙏

[elastic-sonarqube]

Quality Gate passed

Issues
1 New issue
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
42.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube