Make valid json when using `wp vuln status --format=json`

[phlbnks]

This command outputs multiple JSON lists, yet it's reasonable to expect a single output in JSON; what's more you have to use --quiet to avoid text string being output too. This outputs a single valid JSON array that merges all 3 outputs.

[jeffpaul]

@TheLastCicada @jasondewitt pinging you to see if this is something you still want to get into the plugin / have feedback before its ready to be merged?

[jeffpaul]

Confirmed with @kojraai that this PR looks good and provides a valid JSON file

wp vuln plugin-status --format=json | jq .
[
  {
    "name": "wpcli-vulnerability-scanner/wpcli-vulnerability-scanner",
    "installed version": "0.0.3",
    "status": "Error generating report for wpcli-vulnerability-scanner/wpcli-vulnerability-scanner",
    "introduced in": "n/a",
    "fix": "n/a"
  },
  {
    "name": "akismet",
    "installed version": "4.1.12",
    "status": "No vulnerabilities reported for this version of akismet",
    "introduced in": "n/a",
    "fix": "n/a"
  },
  {
    "name": "elasticpress",
    "installed version": "3.5.2",
    "status": "No vulnerabilities reported for this version of elasticpress",
    "introduced in": "n/a",
    "fix": "n/a"
  },
  {
    "name": "hello",
    "installed version": "1.7.2",
    "status": "Error generating report for hello",
    "introduced in": "n/a",
    "fix": "n/a"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web <= 1.5.24 - Authenticated LFI",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.25"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web <= 1.5.22 - Authenticated XSS",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.23"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web <= 1.5.30 - SQL Injection",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.31"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web < 1.5.35 - SQL Injection & XSS",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.35"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.46 - Multiple Cross-Site Scripting (XSS) Issues",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.46"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web < 1.5.55 - Unauthenticated SQL Injection",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.55"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10Web < 1.5.68 - Reflected Cross-Site Scripting (XSS)",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.68"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery by 10web < 1.5.69 - Reflected Cross-Site Scripting (XSS)",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.69"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.69 - Multiple Reflected Cross-Site Scripting (XSS)",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.69"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.67 - Authenticated Stored Cross-Site Scripting via Gallery Title",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.67"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.79 - Stored XSS via Uploaded SVG in Zip",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.79"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.75 - Stored Cross-Site Scripting via Uploaded SVG",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.75"
  },
  {
    "name": "photo-gallery",
    "installed version": "1.5.20",
    "status": "Photo Gallery < 1.5.75 - File Upload Path Traversal",
    "introduced in": "n/a",
    "fix": "Fixed in 1.5.75"
  },
  {
    "name": "streamcast",
    "installed version": "2.0.0",
    "status": "StreamCast < 2.1.1 - Contributor+ Stored Cross-Site Scripting",
    "introduced in": "n/a",
    "fix": "Fixed in 2.1.1"
  },
  {
    "name": "wpcli-vulnerability-scanner/wp-vulnerability-scanner",
    "installed version": "0.0.2",
    "status": "Error generating report for wpcli-vulnerability-scanner/wp-vulnerability-scanner",
    "introduced in": "n/a",
    "fix": "n/a"
  }
]