Inconsistent URL decoding of HttpRequest.Path with percent-encoded characters

### Describe the bug

`HttpContext.Request.Path` seems to decode percent-encoded URLs sometimes, but not all the time. The [documentation](https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.httprequest.path?view=aspnetcore-5.0) says nothing about encoding. I expect it to never decode the path, but testing on ASP.NET Core 3.1 I get results like this:

|Request URL | context.Request.Path |Percent decoded?|
|------------|----------------------|----------------|
|`http://localhost:5000/test%24` |`/test$` |Yes |
|`http://localhost:5000/test%24aa`|`/test$aa` |Yes |
|`http://localhost:5000/test%25a` |`/test%25a` |No |
|`http://localhost:5000/test%25aa`|`/test%aa` |Yes |
|`http://localhost:5000/test%20aa`|`/test%20aa`|No |

### To Reproduce

Create an empty ASP.NET Core project and change the Startup class to

```
public class Startup
{
public void ConfigureServices(IServiceCollection services)
{
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.Use(async (context, next) =>
{
Console.WriteLine("Request path = " + context.Request.Path);
await context.Response.WriteAsync("Request path = " + context.Request.Path);
});
}
}
```

Program class unchanged from the template:

```
public class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}

public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args).ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup(); });
}
```

Then send the above GET requests to it from a web browser or curl.

### Further technical details
- ASP.NET Core version: 3.1
- `dotnet --info`:

```
dotnet --info
.NET SDK (reflecting any global.json):
Version: 5.0.200-preview.21079.7
Commit: 580b1c3770

Runtime Environment:
OS Name: Windows
OS Version: 6.1.7601
OS Platform: Windows
RID: win7-x64
Base Path: C:\Program Files\dotnet\sdk\5.0.200-preview.21079.7\

Host (useful for support):
Version: 5.0.3
Commit: c636bbdc8a

.NET SDKs installed:
3.0.100 [C:\Program Files\dotnet\sdk]
5.0.102 [C:\Program Files\dotnet\sdk]
5.0.103 [C:\Program Files\dotnet\sdk]
5.0.200-preview.21079.7 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.25 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.25 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.25 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.3 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.12 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
```
- The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: VS 16.8.6
- OS: Windows 7 x64