libstore: Add the ability to use different auth methods with Http Binary Caches

[georgyo]

Motivation

Right now the only auth methods allowed with http caches was the default basic auth method. This meant if you wanted to have any other mechanism for authentication you requiring patching the code.

My personal motivation is enabling ?authmethod=negotiate.

Context

This PR is very similar to #10568 but made to be generic and support as many methods from libcurl as we can reasonably support.

Priorities and Process

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