Add MariaDB server example

[sahason]

Signed-off-by: Sonali Saha [email protected]

Description of the changes

Add MariaDB server example

How to test this PR?

Please follow the steps present in mariadb/README.md

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This change is 

[svenkata9]

+1 for @woju 's comment for MariaDB. And, as we discussed last week, we should expand these examples to have secure provisioning, or if that is a bit of stretch, we should at least introduce protected (encrypted) files with wrapped keys as insecure option in the manifest. Gramine-SGX needs to not just run mariadb server in SGX, but also will need to protect the contents of the database.