Move fips/fips-updates pinning to static files

[renanrodrigo]

Instead of creating the pin files dinamically, we ship those as static files (as was decided for ESM) so we a) standardize how we deal with it and b) leverage all apt/dpkg mechanisms to deal with changes in configuration files.

[orndorffgrant]

This idea has gotten high level SRU approval, but needs product/security review to make sure it doesn't have unexpected consequences.