Fix Maven/Gradle Artifacts build.timestamp property

[attiasas]

• All tests passed. If this feature is not already covered by the tests, I added new tests.
• All static analysis checks passed.
• This pull request is on the dev branch.
• I used gofmt for formatting the code before submitting the pull request.

---

At build-info-extractor in ArtifactoryClientConfiguration (at the addDefaultPublisherAttributes method) we sets the timestamp to the buildestarted timestamp if it does not exist:

For Maven and Gradle, when creating properties, we didn't pass a timestamp, so BuildStarted was used.

If a general timestamp was already defined, it was ignored. This PR addresses this issue and passes the correct values.

This issue caused the "undefined/No path found (externally resolved or deleted/overwritten)" error in the Repo path column for Maven and Gradle artifacts with multiple modules:

[eyalbe4]

Before mergint this PR, let's create a PR for an integration test in the jfrog-cli project, or emajnce an existing interation test, to verify this functionality.