Do not join cookies with new like if they weren't before

fix(middleware): ensure headers are wrapped with `Rack::Headers`

Add `Rack::Headers` wrapping to middleware to
prevent header manipulation issues. Added a test
to verify cookies remain as an array when flagged
if already in array format.

While this gem now uses lowercase headers, the Rails default configuration still
defines non-lowercase headers.  As a result, our Railtie will not remove those
conflicting headers.

This change ensures that we're accounting for both lowercase and non-lowercase
default headers in Rails.

CSP3 more explicitly calls this out:

> If path A consists of one character that is equal to the U+002F
> SOLIDUS character (/) and path B is empty, return "Matches".

A URL like `example.com/foo` will match a connect-src of `example.com`,
as well as `example.com/`, so having two connect-srcs listed like this
is redundant.

fix: allow URIs with schema to have trailing slashes normalised

Co-authored-by: Dusty Greif <[email protected]>

Fix rake task file count output message

Co-authored-by: fletchto99 <[email protected]>m>

Co-authored-by: fletchto99 <[email protected]>