Escape backticks when quoting MySQL identifiers

Previously mysql_real_escape_string() was improperly used which escapes
for inclusion in a plain string rather than an identifier.

Also adds basic test support for the DatabaseMysqlBase class.

Co-Authored by: Antoine Musso <hashar@free.fr>
Bug: 55427
Change-Id: Ic045e195c89d8d5d0f0edbda0cd1df781de7025c
Merge "Escape backticks when quoting MySQL identifiers"