refactor(cli): Move cmdflags package under pkg/cli/client

[adodon2go]

What type of PR is this?
cleanup

Which issue does this PR fix:

What does this PR do / Why do we need it:
cmdflags package is used only by pkg/cli/client

If an issue # is not available please add repro steps and logs showing the issue:

Testing done on this change:

Automation added to e2e:

Will this break upgrades or downgrades?
No

Does this PR introduce any user-facing change?:
No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #1840 (b58e862) into main (8c55944) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head b58e862 differs from pull request most recent head 9377f46. Consider uploading reports for the commit 9377f46 to get more accurate results

@@            Coverage Diff             @@
##             main    #1840      +/-   ##
==========================================
+ Coverage   91.72%   91.75%   +0.02%     
==========================================
  Files         143      143              
  Lines       26127    26127              
==========================================
+ Hits        23965    23972       +7     
+ Misses       1597     1591       -6     
+ Partials      565      564       -1     

Files Changed	Coverage Δ
pkg/cli/client/flags.go	100.00% <ø> (ø)
pkg/cli/client/cves_cmd.go	100.00% <100.00%> (ø)
pkg/cli/client/cves_sub_cmd.go	96.90% <100.00%> (ø)
pkg/cli/client/image_cmd.go	92.10% <100.00%> (ø)
pkg/cli/client/image_sub_cmd.go	95.91% <100.00%> (ø)
pkg/cli/client/repo_cmd.go	100.00% <100.00%> (ø)
pkg/cli/client/repo_sub_cmd.go	100.00% <100.00%> (ø)
pkg/cli/client/root.go	100.00% <100.00%> (ø)
pkg/cli/client/search_cmd.go	100.00% <100.00%> (ø)
pkg/cli/client/search_sub_cmd.go	86.76% <100.00%> (ø)
... and 3 more

... and 2 files with indirect coverage changes

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