feat: combine SnapshotTests and SamplesTests

[TimothyMakkison]

Resolves comment in #122

• removed SamplesTests and combined the tests with SnapshotTests
• Added VerifySolution function
• Could merge the methods, opted for this approach in case arguments need to be passed in, in the future.

await Verifier.VerifySolution(source);
await Fixture.VerifyGenerator(source);

[martinothamar]

Thanks!