feat: use gaf sast settings [IDE-724]

[acke]

Description

Changes in Snyk Language Server:

• Snyk Language Server gets the sast settings and the UserAgent from the Go Application Framework Configuration.
• Moved sast_settings.go from /internal/api/contract to local_workflows/code_workflow/sast_contract to be used in snyk-ls.
• Introduced a new constant for the new sast settings called ConfigurationSastSettings in /pkg/local_workflows/code_workflow/native_workflow.go
• Removed references to sastsettings in ApiClient.

Checklist

• Tests added and all succeed
• Linted
• README.md updated, if user-facing
• License file updated, if new 3rd-party dependency is introduced

tests are not mocked now