feat(plugin): add support for nested archives

[knqyf263]

Description

It now works with archives with a root directory, such as GitHub repository archives (cf. #6824 (comment)).

$ wget https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip 
$ unzip main.zip
Archive:  main.zip
383f3f879f103f9f9e587e7dcf475a4f19c4dcf3
   creating: trivy-plugin-referrer-main/
   creating: trivy-plugin-referrer-main/.github/
   creating: trivy-plugin-referrer-main/.github/workflows/
  inflating: trivy-plugin-referrer-main/.github/workflows/release.yaml
  inflating: trivy-plugin-referrer-main/.gitignore
  inflating: trivy-plugin-referrer-main/LICENSE
  inflating: trivy-plugin-referrer-main/README.md
  inflating: trivy-plugin-referrer-main/get.go
  inflating: trivy-plugin-referrer-main/go.mod
  inflating: trivy-plugin-referrer-main/go.sum
  inflating: trivy-plugin-referrer-main/goreleaser.yml
  inflating: trivy-plugin-referrer-main/list.go
  inflating: trivy-plugin-referrer-main/main.go
  inflating: trivy-plugin-referrer-main/plugin.yaml
  inflating: trivy-plugin-referrer-main/put.go
  inflating: trivy-plugin-referrer-main/tree.go
  inflating: trivy-plugin-referrer-main/types.go

Before

$ trivy plugin install https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip
2024-06-03T21:50:12+04:00       INFO    [plugin] Installing the plugin...       src="https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip"
2024-06-03T21:50:13+04:00       FATAL   Fatal error     plugin install error: failed to load the plugin metadata: file open error: open /var/folders/9_/3y18vrrs5bz6gbkq0kc_4fv80000gn/T/trivy-plugin4290039740/plugin.yaml: no such file or directory

After

$ trivy plugin install https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip
2024-06-03T21:49:12+04:00       INFO    [plugin] Installing the plugin...       src="https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip"
2024-06-03T21:49:16+04:00       INFO    [plugin] Plugin successfully installed  name="referrer" version="0.3.1"

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[DmitriyLewen]

LGTM