Migrate the Package to support AGP 8+

[KhushalJangid]

Flutter version: 3.24.5
Java version: 21
Gradle version: 8.5

The flutter engine throws this error:

A problem occurred configuring project ':flutter_secure_storage'.

Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
Namespace not specified. Specify a namespace in the module's build file. See https://d.android.com/r/tools/upgrade-assistant/set-namespace for information about setting the namespace.

We will need to add this namespace property to the build.gradle of the package