feat: fix GetMicrosoftMulti nil pointer dereference and add GetDebianMulti, GetUbuntuMulti

[MaineK00n]

What did you implement:

If CVE==nil in GetMicrosoftMulti in RDB, do not register it.
refs. #79

Also, GetDebianMulti and GetUbuntuMulti are implemented.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

$ gost server --dbtype sqlite3 --dbpath ./gost.sqlite3
$ curl -H "Content-type: application/json" -X POST -d '{"cveIDs": []}' http://127.0.0.1:1325/microsoft/multi-cves | jq . // empty CVEIDs
$ curl -H "Content-type: application/json" -X POST -d '{"cveIDs": ["CVE-0000-0000", "CVE-2021-38642"]}' http://127.0.0.1:1325/microsoft/multi-cves | jq . // contains invalid CVEID

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES

Reference