Fix pnpm and yarn lock file detection

[konstantinas1]

This PR aims to fix issues described in #1642.

When a pnpm-lock.yaml or yarn.lock files are not present in the root directory cdxgen fails to detect them. This causes cdxgen to try and install dependencies without using the lock file in the first place.

To reproduce on v11.1.8 have a pnpm-lock.yaml file in /frontend and run: CDXGEN_DEBUG_MODE=debug cdxgen $(pwd)

Scanning /Users/konstantin/Documents/GitHub/my-app
Performing babel-based package usage analysis with source code at /Users/konstantin/Documents/GitHub/my-app
Executing 'pnpm install' in /Users/konstantin/Documents/GitHub/my-app/frontend
pnpm install has failed. Generated SBOM will be empty or with a lower precision.

Cdxgen fails to detect the lock file and tries to install dependencies based on package.json.
Same problem exists for yarn.lock.

[prabhu]

Thank you!