dnsdist: Add more build-time options to select features

[rgacogne]

Short description

This PR adds build options to disable the following feature at build time, making it easier to build a customized dnsdist with only the required features:

• OCSP stapling
• credentials hashing
• false sharing padding
• Next Protocol Negotiation

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[omoerbeek]

Checked the balancing of preprocessor conditionals and it looks good.