rename import, implement attestation, cleanup name

[mchmarny]

Major refactor across the entire project to rename the import to vulnerability and implement the attestation import command.

[codecov]

Codecov Report

Merging #20 (06eec54) into main (4910874) will increase coverage by 0.28%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             main      #20      +/-   ##
==========================================
+ Coverage   53.93%   54.21%   +0.28%     
==========================================
  Files          11       11              
  Lines         981      976       -5     
==========================================
  Hits          529      529              
+ Misses        435      430       -5     
  Partials       17       17              

Flag	Coverage Δ
unittests	54.21% <60.00%> (+0.28%)	⬆️

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Impacted Files	Coverage Δ
cmd/aactl/cli/attest.go	0.00% <0.00%> (ø)
cmd/aactl/cli/cmd.go	42.00% <ø> (ø)
pkg/attestation/convert.go	0.00% <0.00%> (ø)
pkg/vul/delete.go	0.00% <0.00%> (ø)
pkg/vul/import.go	9.10% <33.34%> (ø)
pkg/attestation/import.go	5.94% <50.00%> (ø)
cmd/aactl/cli/vuln.go	84.22% <100.00%> (ø)
pkg/convert/grype/grype.go	88.47% <100.00%> (ø)
pkg/convert/snyk/snyk.go	93.92% <100.00%> (ø)
pkg/convert/trivy/trivy.go	94.83% <100.00%> (ø)

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