Unhide --auto-{build,deploy,sync} and update debug notes

[briandealwis]

Description

This PR:

1. Unhides the --auto-sync, --auto-build, and --auto-deploy flags for dev and debug.
2. Adds a note about these flags to the debug command helper.
3. Adds a note about these flags to the debug docs.

User facing changes (remove if N/A)

• skaffold dev and skaffold debug support --auto-build, --auto-deploy, and --auto-sync to control how Skaffold reacts to file changes during a development session.

[gsquared94]

lgtm!

[codecov]

Codecov Report

Merging #5347 (e649e3f) into master (c254d25) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5347      +/-   ##
==========================================
+ Coverage   71.80%   71.83%   +0.02%     
==========================================
  Files         392      392              
  Lines       14228    14230       +2     
==========================================
+ Hits        10217    10222       +5     
+ Misses       3259     3258       -1     
+ Partials      752      750       -2     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/flags.go	87.50% <ø> (ø)
cmd/skaffold/app/cmd/debug.go	100.00% <100.00%> (ø)
pkg/skaffold/docker/image.go	79.53% <0.00%> (+1.39%)	⬆️

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[nkubala]

thanks!