Rename __HostHttp- to __Host-Http- for improved compatibility

While a bit uglier, this makes it easier to deploy this to non-supporting browsers while not losing the characteristics that `__Host-` provides.

Tested in web-platform-tests/wpt#54226. Relevant Cookie Store API changes in whatwg/cookiestore#286.

Author: yoavweiss

draft-ietf-httpbis-layered-cookies.md

@@ -679,10 +679,10 @@ This helps developers and server operators to know that the cookie was set using
 a `Set-Cookie` header, and is limited in scope to HTTP requests.
 
 
-#### The "__HostHttp-" prefix
+#### The "__Host-Http-" prefix
 
 If a cookie's name begins with a case-sensitive match for the string
-`__HostHttp-`, then the cookie will have been set with a `Secure` attribute, an
+`__Host-Http-`, then the cookie will have been set with a `Secure` attribute, an
 `HttpOnly` attribute, a `Path` attribute with a value of `/`, and no `Domain` attribute.
 
 This helps developers and server operators to know that the cookie was set using
@@ -1305,7 +1305,7 @@ boolean _httpOnlyAllowed_, boolean _allowNonHostOnlyCookieForPublicSuffix_, and
 
 1. If _cookie_'s name, byte-lowercased, starts with `__http-` and _cookie_ is not Http-prefix compatible, then return null.
 
-1. If _cookie_'s name, byte-lowercased, starts with `__hosthttp-` and _cookie_ is not both Host-prefix compatible and Http-prefix compatible, then return null.
+1. If _cookie_'s name, byte-lowercased, starts with `__host-http-` and _cookie_ is not both Host-prefix compatible and Http-prefix compatible, then return null.
 
 1. If _cookie_'s name is the empty byte sequence and one of the following is true:
 
@@ -1315,7 +1315,7 @@ boolean _httpOnlyAllowed_, boolean _allowNonHostOnlyCookieForPublicSuffix_, and
 
     * _cookie_'s value, byte-lowercased, starts with `__http-`, or
 
-    * _cookie_'s value, byte-lowercased, starts with `__hosthttp-`,
+    * _cookie_'s value, byte-lowercased, starts with `__host-http-`,
 
    then return null.