feat: create temp filepath for iac engine to write results [CFG-2114]

[ipapast]

What does this PR do?

This commit creates a temporary filepath and passes it through the -output flag to the snyk-iac-test executable.
The snyk-iac-test will then write all the results to this file, which the CLI will have to read and present to the user.

Notes:

• the flag is not visible to the user, this will all happen in the background.
• the file is created with empty content on the CLI side, and then gets overwritten by the snyk-iac-test with the results. This comment explains also reasoning about runnings scans in parallel: https://snyksec.atlassian.net/browse/CFG-2114?focusedCommentId=509517
• the file is deleted when the results are read on the CLI side.
• if errors happen during the file creation they will get caught on the CLI side too.
• if errors happen during the file writing we will handle them on the snyk-iac-test side and return with exit code 1 to the CLI.

Use this in combination with https://github.com/snyk/snyk-iac-test/pull/106 to test.

How should this be manually tested?

• Go to the branch of snyk-iac-test above and build locally: go build -o snyk-iac-test .
• Create a bundle in opa-rules repository if you don't have one: make dist
• Then run a scan as usual to see results:
  SNYK_IAC_POLICY_ENGINE_PATH=~/snyk-iac-test/snyk-iac-test SNYK_IAC_BUNDLE_PATH=~/opa-rules/dist.tar.gz snyk-dev iac test test/fixtures/iac/terraform/sg_open_ssh.tf --experimental



[github-actions]

	Warnings
⚠️	You've modified files in src/ directory, but haven't updated anything in test folder. Is there something that could be tested?

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