[now dev] Print Serving all files as static only once

[AndyBitz]

Print Serving all files as static only once, as it will get printed every time a file changes otherwise.

[codecov-io]

Codecov Report

Merging #2590 into canary will increase coverage by <.01%.
The diff coverage is 87.5%.

@@            Coverage Diff             @@
##           canary    #2590      +/-   ##
==========================================
+ Coverage   13.83%   13.83%   +<.01%     
==========================================
  Files         257      257              
  Lines        9356     9365       +9     
  Branches     1057     1060       +3     
==========================================
+ Hits         1294     1296       +2     
- Misses       7940     7947       +7     
  Partials      122      122

Impacted Files	Coverage Δ
src/util/dev/server.ts	64.38% <87.5%> (-0.12%)	⬇️
src/util/metrics.ts	61.53% <0%> (-6.65%)	⬇️
src/util/dev/builder-cache.ts	77.27% <0%> (-1.22%)	⬇️

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