Fix disabling implicit prelude

[rprije]

Setting the default-extension NoImplicitPrelude in .cabal files had no effect. Turning on -Wimplicit-prelude revealed Prelude still gets loaded implicitly. eg:

common/src/Common/Route.hs:1:1: warning: [-Wimplicit-prelude]
    Module `Prelude' implicitly imported

Debugging revealed NoImplicitPrelude was not being included in the LANGUAGE pragma heading added by the ob preprocessor. This is because NoImplicitPrelude in Cabal is considered to be a disabling of the ImplicitPrelude extension and ob was ignoring disabled extensions. This PR adds support for disabled extensions and thus fixes NoImplicitPrelude. It should also fix other similarly treated extensions such as NoMonomorphismRestriction

I have:

• Based work on latest develop branch
• Looked for lint in my changes with hlint . (lint found code you did not write can be left alone)
• Run the test suite: $(nix-build -A selftest --no-out-link)
• (Optional) Run CI tests locally: nix-build release.nix -A build.x86_64-linux --no-out-link (or x86_64-darwin on macOS)

[ali-abrar]

Thanks @rprije