Update docker static resource for dotnet-isolated 8 - Default ASP.NET Core port changed from 80 to 8080

Follow up to https://learn.microsoft.com/en-us/dotnet/core/compatibility/containers/8.0/aspnet-port

Docker template used in Core Tools needs to be updated - [azure-functions-core-tools/src/Azure.Functions.Cli/StaticResources/Dockerfile.dotnet8Isolated at v4.x · Azure/azure-functions-core-tools (github.com)](https://github.com/Azure/azure-functions-core-tools/blob/v4.x/src/Azure.Functions.Cli/StaticResources/Dockerfile.dotnet8Isolated)

to match what you shared above; also, [azure-functions-core-tools/src/Azure.Functions.Cli/StaticResources/Dockerfile.dotnet8Isolated at v4.x · Azure/azure-functions-core-tools (github.com)](https://github.com/Azure/azure-functions-core-tools/blob/v4.x/src/Azure.Functions.Cli/StaticResources/Dockerfile.dotnet8Isolated#L1) is still pointing to preview - needs to be updated as well

```
FROM mcr.microsoft.com/azure-functions/dotnet-isolated:4-dotnet-isolated8.0 AS base
WORKDIR /home/site/wwwroot
EXPOSE 8080
```

Open src/Azure.Functions.Cli/StaticResources/Dockerfile.dotnet8Isolated and compare it with the linked .NET 8 ASP.NET Core container guidance. Update the base image reference from preview and expose port 8080; done means the static Dockerfile matches the requested FROM, WORKDIR, and EXPOSE lines.

Written by the indexing model from the issue text.