fix(cli): restore ability to read manifests from stdin

[krancour]

Fixes #1713 and reverts/replaces what was done in #1539

[netlify]

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Name	Link
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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 37 lines in your changes are missing coverage. Please review.

Project coverage is 44.18%. Comparing base (f696589) to head (6efee8d).

Files	Patch %	Lines
internal/cli/option/kubernetes.go	0.00%	25 Missing ⚠️
internal/cli/option/flag.go	0.00%	5 Missing ⚠️
internal/cli/cmd/apply/apply.go	0.00%	3 Missing ⚠️
internal/cli/cmd/create/create.go	0.00%	2 Missing ⚠️
internal/cli/cmd/delete/delete.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1715      +/-   ##
==========================================
- Coverage   44.37%   44.18%   -0.20%     
==========================================
  Files         206      207       +1     
  Lines       13108    13090      -18     
==========================================
- Hits         5817     5784      -33     
- Misses       7041     7065      +24     
+ Partials      250      241       -9     

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[hiddeco]

I count not depending on kubectl still as a major improvement, even if this is a second attempt 💯