Combines the 2 time values in the HSTS entry with a single timestamp for
expiration. (9MB savings per list)
The previous time representations were based on system boot time which
meant that the `hsts_list.json` round trip across boots resulted in
completely erroneous expiration times.
The preload list is now initialized separately from the public and
private lists and shared by both, cutting memory use in half.
Overall takes memory use from 64MB for HSTS to 24MB.
Expired HSTS entries are now removed from the list when updating an
entry and subdomains can be added to a list if the superdomain does not
already include them.
Testing: New unit tests added
Related to #25929 but the next step would be to attempt to use
https://github.com/BurntSushi/fst Which will be explored in a follow-up.
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Signed-off-by: Sebastian C <sebsebmc@gmail.com>
103cbed928