What does this implement/fix?

Two changes:

• Show load instead of CPU % in info box as this (a) is more meaningful (naturally includes IOWait, etc.) and (b) is what we have shown in v5 as well so users are used to seeing these values even if they are less intuitive than CPU % at first
• Still show total CPU % on settings / system info tab for easy contrasting to the CPU % used by FTL

Needs FTL branch new/total_cpu to work pi-hole/FTL#2297

Related issue or feature (if applicable): Fixes #3261

Pull request in docs with documentation (if applicable): N/A

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