reduce noise of log output

[luhring]

This PR dials down the severity of log entries that tend to be hit during common scanning scenarios.

For example, during any project (directory) scans on my macOS machine, I see these log entries every time:

[0008]  WARN directory resolver unable to evaluate symlink for path="/etc/os-release" : lstat /Users/dan/Source/grype-vscode/etc: no such file or directory
[0008]  WARN directory resolver unable to evaluate symlink for path="/usr/lib/os-release" : lstat /Users/dan/Source/grype-vscode/usr: no such file or directory
[0008]  WARN directory resolver unable to evaluate symlink for path="/etc/system-release-cpe" : lstat /Users/dan/Source/grype-vscode/etc: no such file or directory
[0008]  WARN directory resolver unable to evaluate symlink for path="/etc/redhat-release" : lstat /Users/dan/Source/grype-vscode/etc: no such file or directory
[0008]  WARN directory resolver unable to evaluate symlink for path="/bin/busybox" : lstat /Users/dan/Source/grype-vscode/bin: no such file or directory

Additionally, since we're now showing INFO lines by default, Syft has been showing some log lines even with the TUI view that probably don't need to be exposed to users during every run. I've reduced these log instances to DEBUG.

Helps with anchore/grype#684 by removing Syft log entries from routine scanning use cases.

[spiffcs]

I think I'd still like to see:

[0000]  INFO syft version: [not provided]
[0000]  INFO identified distro: Alpine Linux v3.15
[0000]  INFO cataloging image

Provided if someone passes the -v flag to syft. Having INFO and DEBUG are helpful to provide finer layers of detail for users. INFO is always a good first stop to check things and then can progress to -vv.

Currently this change makes it so that