Add the theme type (block theme or non block theme) to the site health page

[sebastienserre]

Hello,

Now 2 types of theme are running in the WordPress ecosystem, I think we should add a mention in the Site Health.

Something like Block theme: true/false

Because a block theme is not managed like a "classic" one, it can be useful to adapt our help.
For example, about a menu issue, there's no more Menu item in Appreance with Block theme

Trac ticket: https://core.trac.wordpress.org/ticket/62526

### Description

This PR adds theme check and display whether the theme is block based or not.

### Expected behaviour

In site health, it should display whether the theme is block based or not.

### Screenshots/Screencasts

Thanks @benazeer-ben for the PR. Below is the test report.

## Test Report
### Description
This report validates whether the indicated patch works as expected.

Patch tested: Tested the changes in this PR and it works as expected.

### Environment

• WordPress: 6.8-alpha-59274-src
• PHP: 8.2.25
• Server: nginx/1.27.2
• Database: mysqli (Server: 8.0.40 / Client: mysqlnd 8.2.25)
• Browser: Chrome 131.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.0
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

### Actual Results

1. ✅ Theme Status is added with this PR

### Screenshot