Rename our HTP pools

Originally created by @intrigeri on #15428 (Redmine)

People get confused by the use of pal/neutral/foe. We should rename these variables and update https://tails.boum.org/contribute/design/Time_syncing/ to clarify that we don’t really need to trust even the “pal” pool, what we need is low chances of members of different pools conspiring against our users.

Feature Branch: feature/15428-rename-htp-pools, htp:feature/15428-rename-htp-pools

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