Test OCI8 on CI

[nikic]

The oci8 extension is currently not tested on CI. Per php/php-src#5714 (comment) it used to be tested on gcov, but gcov is no longer used since PHP 7.4.

To test oci8, we need to have OracleDB XE available on one of our public CI providers (Travis, Azure Pipelines or AppVeyor). It seems like this is not really possible right now (in a legal way), but based on the discussion in oracle/docker-images#1156 it might be possible in the future.

[nikic]

We now at least test that OCI8/PDO_OCI build (#29).

[mvorisek]

This issue can be closed, CI for oci8/pdo_oci was added by me in php/php-src#8348

[mvorisek]

@kocsismate should be also marked as done in #29