Fixes #22

Checklist

• I have read the Contribution Guide ;
• There is an approved issue describing the change when contributing a new analyzer or suppressor ;
• I have added tests that prove my fix is effective or that my feature works ;
• I have added necessary documentation (if appropriate) ;

Short description of what this resolves:

Detects expensive calls to GetComponents and Camera.main in Update and FixedUpdate and provides a codefix to cache the results instead.

TODO

• Detect expensive calls to GetComponent in Update and FixedUpdate
• Detect expensive access to Camera.main in Update and FixedUpdate
• Refactor similar code in CacheExpensiveCalls.cs to have one path before branching to InvocationExpression and MemberAccessExpression
• Create helper class for shared code between analyzers
• Provide a code fix that caches these calls in Awake instead
• Ensure the code fix wont write duplicated code if the expensive call is already cached, for whatever reason. That would break user's build.
• Write tests
• Write docs