x/pkgsite: condense display of vulnerabilities on module pages

[tatianab]

[gopherbot]

Change https://go.dev/cl/597176 mentions this issue: static/frontend: condense display of vuln chips

[gabyhelp]

Related Issues and Documentation

• x/pkgsite: surface known vulnerabilities for a module version #56205
• x/pkgsite: add package/module path to pkg.go.dev/vuln/list #52685 (closed)
• x/pkgsite: integrate with Go vulnerability database #48223 (closed)

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