Add FIPS build.

[joshdrake]

This PR adds a new Dockerfile using an Alpine base with OpenSSL compiled in FIPS-mode and a binary built with boringcrypto.

💔Thank you!

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[maraino]

We should use tags and add a file like this:

//go:build fips
// +build fips

package something

import _ "crypto/tls/fipsonly"

[hslatman]

Closing this, as it has been solved in a different way.