Initial basic build for core

[sdavtaker]

• Improving main CMakeLists code organization
• Removing dependencies from gitignore
• Moving from test to tests for integration tests location
• Basic core build

Issue #1888 , if available:

Description of changes:
First build for core library, it follow simple linux/mac config with defaults only. Crt mocked for testing.

Check all that applies:

• Did a review by yourself.
• Added proper tests to cover this PR. (If tests are not applicable, explain.)
• Checked if this PR is a breaking (APIs have been changed) change.
• Checked if this PR will not introduce cross-platform inconsistent behavior.
• Checked if this PR would require a ReadMe/Wiki update.

Check which platforms you have built SDK on to verify the correctness of this PR.

• Linux
• Windows
• Android
• MacOS
• IOS
• Other Platforms

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