Update and give reasons for calling cmake.install() in package()

[danimtb]

Coming from conan-io/conan#4918, I realized no reasons are given on this how to https://docs.conan.io/en/latest/howtos/cmake_install.html to use the package() instead fo the build().

We could explain a little bit that and argument the following cases:

• Usage of conan create --keep-build
• Usage of local development flow

[uilianries]

should we consider configure_cmake helper?

[danimtb]

What you mean? The helper function? I think it is already suggested in the example