Support for MySQL

[ernstc]

Data inspector should be available also for MySQL databases.

The analysis of the extension below can be useful for the implementation of this feature:
https://github.com/microsoft/azuredatastudio-mysql

[ernstc]

Queries for retrieving metadata about schemas, tables and columns.

-- Get the list of schemas
SELECT * FROM information_schema.schemata;

-- Get the list of tables
SELECT * FROM information_schema.tables WHERE table_schema = 'mydb';

-- Get the list of columns
SELECT * FROM information_schema.columns WHERE table_schema = 'mydb' AND table_name = 'test';

-- Get the list of table columns with their data types and primary keys
SELECT 
    ordinal_position, 
    column_name, 
    data_type, 
    character_maximum_length, 
    is_nullable, 
    column_key 
FROM 
    information_schema.columns 
WHERE 
    table_schema = 'mydb' AND table_name = 'test';