Integrate Cadence testing framework to the CLI

[SupunS]

Work towards onflow/cadence#331

Description

This PR is to integrate the new Cadence testing framework into the CLI.

Command:

flow test /path/to/test_script.cdc

Sample output:

Running tests...

Test results:
- PASS: testImportingContract
- PASS: testSimpleScript
- PASS: testSimpleTransaction
- FAIL: testAssertionFailure
		assertion failed: manually failed the test case
- PASS: testInvokingContractFunction
- PASS: testReadingFile
- FAIL: testDeployingContractWithImports
		panic: [Error Code: 1101] cadence runtime error Execution failed:
			error: cannot deploy invalid contract
			 --> 9df24568a2615ba869f4b00abde9fb17f9b1ebe1d3cdd45d3f191f7d579e415e:4:7

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[devbugging]

@SupunS this is really awesome!!! 🔥 Thank you. Left some comments but nothing major. The one thing that is also lacking is documentation. Make sure to add that as you finish things up.

[SupunS]

@sideninja I'll open a separate PR to add documentation, so that this PR doesn't get too big.

[devbugging]

The only question left here is, should we have this as top commands or not? why this changed from last time you were working on it is because I believe we will also add linter, so I'm now wondering should those commands be flow test flow lint or flow cadence test flow cadence lint. In some way lint and test are indicating doing that for flow so in some sense that is justifiable to be as a top-level command. Do you have opinion?

[SupunS]

I'm happy with either way.

I'm slightly leaning towards having the test command at the top-level, because it's not only a cadence-related command, but also involves other aspects of flow (uses flow.json, test cases may actually test all blockchain-related operations, etc.).

But for some of the other tools like lint, and maybe document-generator (in future), grouping them under cadence makes sense, because they are very cadence specific.

[turbolent]

Nice work!

[devbugging]

Looks good. Thank you! Nice work