HTTPCookie: parse domain according to RFC

[drodriguez]

When the domain field is specified, the cookie is intended for the
domain and subdomains, so the value of domain has to be prefixed by a
dot.

Added tests to check for this behaviour and modified the incorrect
tests.

NOTE: I checked this behaviour in macOS 13.14.5, and it matches Foundation there.

[drodriguez]

@swift-ci please test

[pushkarnk]

@swift-ci please test

[millenomi]

@swift-ci please test

[millenomi]

@drodriguez This patch needs conflict resolution before merging.

[drodriguez]

Conflicts resolved.

@swift-ci please test Linux platform

[spevans]

@swift-ci test linux

[drodriguez]

@swift-ci please test Linux platform

[compnerd]

This broke the Windows build :-(. https://dev.azure.com/compnerd/windows-swift/_build/results?buildId=4605&view=logs&j=b9e62f99-1a98-5ed7-01d2-f4794231ed79

D:/a/1/s/swift-corelibs-foundation/Foundation/HTTPCookie.swift:622:17: error: use of unresolved identifier 'in_addr'
        var x = in_addr()
                ^~~~~~~
D:/a/1/s/swift-corelibs-foundation/Foundation/HTTPCookie.swift:623:16: error: use of unresolved identifier 'inet_pton'
        return inet_pton(AF_INET, string, &x) == 1
               ^~~~~~~~~
D:/a/1/s/swift-corelibs-foundation/Foundation/HTTPCookie.swift:623:26: error: use of unresolved identifier 'AF_INET'
        return inet_pton(AF_INET, string, &x) == 1
                         ^~~~~~~

[drodriguez]

I saw that yesterday. I was trying to rebuild everything in Windows to try to fix it. It might be a missing import of WinSDK, or a slightly different functiin name. I will try to finish that today.