test: fix input tests with expect not covering false negatives

[ttytm]

expect itself doesn't return an exit code based on whether the input is correct or not.
Therefore the current tests for command line input using expect will always return exit_code == 0.

The changes fix and extend the test coverage. They include tests that should fail, update towards being directory independent and using regular V tests.

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Additional info that might save some time while testing/reviewing

Example to reproduce the issue locally at current master:

Current related CI for reference:

v/.github/workflows/linux_ci.yml

Lines 102 to 104 in 322ba71

	run: |
	./v examples/password
	./v examples/password/password_ci.vsh

To simplify the following steps move from your vroot into cd examples/password/ and comment out chdir in password_ci.vsh

// password_ci.vsh

// chdir('examples/password')!  // <- comment out 
assert execute('./correct.expect').exit_code == 0
assert execute('./incorrect.expect').exit_code == 0

Run the test v ./password_ci.vsh -> should pass.

Change an expected value in ./correct.expect. E.g.:

- expect "Enter your password : "
+ expect "Wrong Expect : "

Re-running the test v ./password_ci.vsh will also pass after a short timeout. But it should not pass 🧙🏽‍♂️.