perf(helm): load in-memory files

[nikpivkin]

Description

Instead of copying files to a temporary folder, we can pass virutal files to helm, which improves performance.

benchstat old.txt new.txt
goos: darwin
goarch: arm64
pkg: github.com/aquasecurity/trivy/pkg/iac/scanners/helm/test
                    │   old.txt    │               new.txt               │
                    │    sec/op    │   sec/op     vs base                │
_RenderChartFiles-8   2138.1µ ± 2%   978.3µ ± 3%  -54.24% (p=0.000 n=10)

                    │   old.txt    │               new.txt               │
                    │     B/op     │     B/op      vs base               │
_RenderChartFiles-8   570.4Ki ± 0%   532.8Ki ± 0%  -6.59% (p=0.000 n=10)

                    │   old.txt   │              new.txt               │
                    │  allocs/op  │  allocs/op   vs base               │
_RenderChartFiles-8   7.714k ± 0%   7.476k ± 0%  -3.09% (p=0.000 n=10)

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[simar7]

nice!

[simar7]

@nikpivkin just curious if there's any special handling that we need to perform with symlinks, or would this work with that as well?

[nikpivkin]

@simar7 As far as I know, Trivy skips non-regular files, so they don't get into the virtual file system that post analysers work with.

[simar7]

OK let's merge it in v0.51.0