The .ostc-ci directory becomes .oniro-ci

The various CI variables names are now all uniformly named CI_ONIRO_.
Some specific variables were further trimmed to avoid using "CI" twice.

Remaining uses of OSTC and OHOS are for URLs, container images and
branch names.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>