Previously CGIT_CLONE_PREFIX_(PHP|FASTAPI), we found that we could
use the same env var in multiple places, including non-cgit-clone-prefix
areas.

So, they were renamed, and one additional prefix was added.

- CGIT_CLONE_PREFIX_PHP -> AURWEB_PHP_PREFIX
    - Used for cgit's clone prefix and AUR_CONFIG's aur_location for PHP
- CGIT_CLONE_PREFIX_FASTAPI -> AURWEB_FASTAPI_PREFIX
    - Used for cgit's clone prefix and AUR_CONFIG's aur_location for FastAPI
- AURWEB_SSHD_PREFIX
    - Used for aurweb's sshd clone prefix shown on package pages

Signed-off-by: Kevin Morris <kevr@0cost.org>