Update udaru-hapi-plugin dependencies to the latest @hapi scope to fix a vulnerability issue

[allbto]

When running npm audit on my node project I received:

                       === npm audit security report ===

┌──────────────────────────────────────────────────────────────────────────────┐
│                                Manual Review                                 │
│            Some vulnerabilities require your attention to resolve            │
│                                                                              │
│         Visit https://go.npm.me/audit-guide for additional guidance          │
└──────────────────────────────────────────────────────────────────────────────┘
┌───────────────┬──────────────────────────────────────────────────────────────┐
│ High          │ Denial of Service                                            │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Package       │ subtext                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Patched in    │ No patch available                                           │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Dependency of │ @nearform/udaru-hapi-plugin                                  │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Path          │ @nearform/udaru-hapi-plugin > hapi > subtext                 │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ More info     │ https://npmjs.com/advisories/1168                            │
└───────────────┴──────────────────────────────────────────────────────────────┘
found 1 high severity vulnerability in 3627 scanned packages
  1 vulnerability requires manual review. See the full report for details.

There are no way to fix this issue on my own, because hapi and subtext dependencies are not maintained (they moved to @hapi/hapi and @hapi/subtext), therefore the npm audit fix command couldn't solve the issue. The only way to fix it is to update the @nearform/udaru-hapi-plugin dependencies.

In this PR I've updated the following dependencies:

• "boom": "^7.2.2" -> "@hapi/boom": "^8.0.1"
• "hoek": "^6.1.3" -> "@hapi/hoek": "^8.3.0"

And I noticed that the hapi package was only used in tests and not in the main code, so I moved "hapi": "^18.1.0" to devDependencies as "@hapi/hapi": "^18.4.0".

I've also updated the devDependencies:

• "code": "^5.2.4" -> "@hapi/code": "^6.0.0"
• "lab": "^18.0.2" -> "@hapi/lab": "^20.4.0"

Let me know if anything else is needed in order to merge this PR.

[coveralls]

Coverage remained the same at 94.086% when pulling a225baf on allbto:fix/hapi-plugin-libs-scope into 09cf319 on nearform:master.

[mcollina]

LGTM