Lack of test on Travis for PHP 7.4 and tests don't run on upcoming PHP versions

[pawelkg]

Describe the bug
For now Travis configuration have not set test for PHP 7.4. Other problem is that tests on upcoming PHP version won't run.

CodeIgniter 4 version
RC2.1

Affected module(s)
none

[jim-parry]

This both an issue and a PR? We don't need both.
Why do we need to test PHP7.4 & nightly? The build takes a while as it is, and it is likely to be some time before we look at taking advantage of them.

[pawelkg]

For now tests are take for nightly only. I assume that initially at target to PHP 7.4. Now nightly is future version of PHP 8.
Other thing is that now tests for version > 7.3 do not run at all, because composer can not install all packages because of dependencies.
Because PHP7.4 will be released in about month, I think that it's reasonable to make test for this version and prepare to this.

[lonnieezell]

We were just discussing this one, actually. The matrix is too unweildy to deal with if we don't have to. I think dropping nightly for now and keeping 7.4 as an allowed_failure is workable.

According to a comment on this post over at Travis, we can use 7.4snapshot might allow us to get that working.

[pawelkg]

I update my PR to work with PHP 7.4 (no snapshot) as it's avaliable right now on Travis.
@lonnieezell I wonder if there is a way to change tests to run all databases specified in some file on one pass. That way we will not need to run one travis instance for each driver. As @jim-parry point out, now test take a long time. When there will be more database drivers and more PHP versions to test, there will be easier to test all drivers in one run. In summary that approach should take less time.

[MGatner]

7.4 is working from #2514 - a larger pass at the testing service and matrix framework would probably be involved in a refactor.