Fix MVC and Razor Pages scoped CSS styling for project names with spaces

[Copilot]

This PR extends the fix from #62675 (Blazor scoped CSS space handling) to MVC and Razor Pages templates, ensuring that projects with spaces in their names have correctly functioning scoped CSS.

Problem

When creating MVC or Razor Pages projects with spaces in their names (e.g., "My Web App"), the scoped CSS bundle reference breaks because the hardcoded Company.WebApplication1.styles.css reference doesn't match the actual generated bundle name, which sanitizes spaces to underscores.

Solution

Applied the same StyleBundleName generator pattern used in the Blazor fix:

1. Added StyleBundleName generator to both template.json files that uses regex to replace spaces with underscores:

   "StyleBundleName":{
     "type": "generated",
     "generator": "regex",
     "replaces": "StyleBundleName",
     "parameters": {
       "source": "name",
       "steps": [
         {
           "regex": " ",
           "replacement": "_"
         }]
     }
   }

2. Updated _Layout.cshtml files to use the dynamic StyleBundleName:

   <!-- Before -->
   <link rel="stylesheet" href="~/Company.WebApplication1.styles.css" asp-append-version="true" />
   
   <!-- After -->
   <link rel="stylesheet" href="~/StyleBundleName.styles.css" asp-append-version="true" />

Testing

• ✅ Template JSON validation passes
• ✅ Integration tests verify correct CSS references for projects with spaces
• ✅ Edge cases tested (multiple spaces, leading/trailing spaces, etc.)
• ✅ Build system compiles templates successfully

Example

For a project named "My Web App":

• Old: References Company.WebApplication1.styles.css (broken)
• New: References My_Web_App.styles.css (works correctly)

This ensures that scoped CSS styling works consistently regardless of whether the project name contains spaces.

Fixes #62679.

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[dotnet-policy-service]

Greetings human! You've submitted a PR that modifies code that is shared with https://github.com/dotnet/runtime . Please make sure you synchronize this code with the changes in that repo!

[javiercn]

@MackinnonBuck @joperezr in case you folks want to take this. @dariatiurina fixed it for Blazor.