trivy: bugfix: line reported as col; bugfix: crash on missing line from trivy; plus refinements

[bobsrac]

Changes

• bugfix: no longer reports trivy StartLine, EndLine as nvim-lint col, end_col
• bugfix: check parsed fields before building/inserting diagnostic
• cleanup: fix deprecated CLI arg: '--scanners config' -> '--scanners misconfig'
• comments: clarify intent to ease future maintainence

Bug Descriptions

Output from trivy sometimes includes line info, but not column info. line info is used for both col and lnum in trivy.lua

Output from trivy does not always contain StartLine and EndLine fields. When they are missing, diagnostics are not created for each Misconfiguration from trivy, but instead a single diagnostic is generated with a lua error about accessing a nil value (StartLine).

To reproduce, open the following Dockerfile with trivy enabled as a linter, then look at the reported diagnostics:

FROM ubuntu:24.04
LABEL maintainer="John Doe <john.doe@aol.com>"