curl: enable libpsl

[samueloph]

Build with libpsl to turn on Public Suffix List checks, so cookies can't be set for broad public suffixes like .co.uk; this blocks "supercookies" that would otherwise be shared across unrelated sites under the same suffix.

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[samueloph]

Feel free to take over this PR to address any pending issues, my motivation was to point out that PSL is not enabled (very likely by mistake) and the PR was simple enough, but I don't plan on spending more time on this, sorry.

[bagder]

As a curl maintainer, I can only say 👍

PSL should be enabled by default methinks.

[Bo98]

Looks good but we probably need rockdaboot/libpsl#257 to make it to a release first otherwise curl will require Python.

very likely by mistake

I believe this was raised once before and the Python requirement was the main issue, but looks like it's fixed now (but with no release yet).