feat(license): scan vendor directory for license for go.mod files

[DmitriyLewen]

Description

There are cases when users use only vendor dir (go mod vendor) command.

For these cases we can't detect licenses from $GOPATH/pkg/mod dir.

New logic

graph TD
    A[Detect licenses for go.mod files] --> B{vendor direxists?}
    B -- yes --> C[use vendor dir to find licenses]
    B -- no --> D[use $GOPATH/pkg/mod]

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Discussed in #8517