fix: exclude-base-image-vulns to work with autodetected base image

[RotemS]

• [x] Follows CONTRIBUTING rules

What does this PR do?

Fixes an issue where --exclude-base-image-vulns does not work properly when the base image is auto detected, without using --file

How should this be manually tested?

snyk container test alpine:3.10 with/without --exclude-base-image-vulns

[github-actions[bot]]

	Warnings
:warning:	Since the CLI is unifying on a standard and improved tooling, we're starting to migrate old-style imports and exports to ES6 ones. A file you've modified is using either module.exports or require(). If you can, please update them to ES6 import syntax and export syntax. Files found: src/lib/snyk-test/legacy.ts

Generated by :no_entry_sign: dangerJS against 5daf6912b1c30256c1a2dec507d47d321890ae44

[shaninja]

my updates:

1. stop tests from blowing up by adding optional chaining to dockerRes.baseImage
2. added vuln info to fake-server in a manner that would enable us to test excluding base image vulns (PS, I am not very prod in the manner that it's done. welcoming suggestions!)
3. made sure that has no vulns with flag without a dockerfile tests failed if code is reverted to the way it was before

note: I added the tests under the windows exclusion. the current --exclude-base-image-vulns test was already there, and those tests do in fact don't pass the windows suite. not entirely sure why it's needed. dropped a question in the commit that introduced it.

[thisislawatts]

🧹 Closing as stale.