chore(cli): introduce EOL message

[odubajDT]

This PR

• adds EOL message to each CLI command

Related Issues

Part of: #9733

How to test

1. Build cli with go build . -o keptn
2. Execute any command, for example ./keptn auth

[codecov]

Codecov Report

Merging #9741 (29046d2) into master (e332b8a) will decrease coverage by 0.03%.
Report is 1 commits behind head on master.
The diff coverage is 44.44%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9741      +/-   ##
==========================================
- Coverage   70.91%   70.88%   -0.03%     
==========================================
  Files         618      618              
  Lines       32731    32738       +7     
  Branches     1645     1645              
==========================================
- Hits        23210    23207       -3     
- Misses       8276     8283       +7     
- Partials     1245     1248       +3     

Files Changed	Coverage Δ
cli/cmd/root.go	71.13% <0.00%> (-0.75%)	⬇️
cli/pkg/config/cli_config.go	55.68% <50.00%> (-0.42%)	⬇️

... and 1 file with indirect coverage changes

Flag	Coverage Δ
cli	44.46% <44.44%> (-0.14%)	⬇️

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication