Baseline tests should check for all possible extensions of not expected files

[ilonatommy]

After #62593 renamed some template files, we could see additional files in templates structure. It could be visible only locally, in case the repository run template tests before and after the PR got in.

This revealed one issue with baseline tests: they would not fail, even if repository was creating a template with incorrect application structure, with three .csproj files instead of only one.

In the particular case of such rename, this behavior would not have been caught by the developer applying the change - for them, the additional dirs would not exist. This change does not aim at improving cleaning the repo from old assets. It is trying to fix possible other cases when we would have additional contents of extensions that we don't currently check for. Maybe there's a good reason we're not doing that. Currently, I don't see it, so I am posting this update.

Description

• Tests: Baseline tests should check for all the types of "not expected" contents, regardless of extension. Skipping bin and obj dirs should stay.

Fixes #62746

[Copilot]

Pull Request Overview

This PR fixes a regression in the template baseline tests by removing redundant file extension checks when determining which files to skip during template validation. The change specifically removes filtering for .csproj, .fsproj, .props, .sln, and .targets files, while preserving the exclusion of bin and obj directories.

• Removes hardcoded file extension filters from baseline test logic
• Maintains existing bin and obj directory exclusion patterns
• Aligns with the stated goal of checking all "not expected" contents regardless of extension