feat(ui): Allow specifying whether local or all snapshots are shown by default

[PhracturedBlue]

When I connect to the server http page, I prefer to see all snapshots shown by default. every time I switch away and come back I need to reselect 'All' instead of 'Local'. This just makes the default a preference option.

Requires kopia/htmlui#186

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (741fbd4) 75.67% compared to head (3560137) 75.65%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3289      +/-   ##
==========================================
- Coverage   75.67%   75.65%   -0.02%     
==========================================
  Files         460      460              
  Lines       36852    36852              
==========================================
- Hits        27888    27882       -6     
- Misses       7036     7040       +4     
- Partials     1928     1930       +2     

see 7 files with indirect coverage changes

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[PhracturedBlue]

I noticed that this will result in a configuration setting that has no effect when using the kopiaUI application (since multiUser is false there).

Solutions:

• keep the code as is
• leave the setting always available and place it in a 'multi user' section
• query multi-user mode on the preferences page and hide the config option
• remove the config option altogether and default to 'All Snapshots' if there is no local snapshot

The last option cold be done entirely in the UI without a need for any server-side changes, but it is the least flexible.