New Rule: should not compare two different types

[nunnatsa]

The Equal and the BeIdentical matchers also check the type, not only the value.

The following code will fail in runtime:

x := 5 // x is int
Expect(x).Should(Eqaul(uint(5)) // x and uint(5) are with different
types

When using negative checks, it's even worse, because we get a fale positive:

x := 5
Expect(x).ToNot(Equal(uint(5))

To solve this problem, we want to find these errors before running the tests and failing on runtime. This is even more important for e2e or functional tests, where we sometimes can't run them on the local development environment.

This PR adds a new rule to the linter, to find comaprison of values from different types.

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Added test case and related test data
• [x] Update the functional test

Checklist:

• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I ran golangci-lint

@pohly

fixes #109

[github-actions[bot]]

Pull Request Test Coverage Report for Build 6369713012

• 69 of 82 (84.15%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 83.844%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
types/config.go	8	10	80.0%
ginkgo_linter.go	61	72	84.72%
<!--	Total:	69	82	84.15%	-->

Totals
Change from base Build 6141414406:	-0.1%
Covered Lines:	986
Relevant Lines:	1176

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💛 - Coveralls