Create Better Encapsulated Constructors for each Database

[VinGarcia]

This release adds new constructor functions that should make it simpler to start using the project.

Before this release the user would have to import a database/sql driver such as _ "github.com/denisenkom/go-mssqldb" when he wanted to SQLServer, SQLite or MySQL.

Now we have separated packages for each database allowing the user to simply import that package to start using that version of the adapter, e.g.:

• db, err := kpgx.New(ctx, connURL, ksql.Config{})
• db, err := kmysql.New(ctx, connURL, ksql.Config{})
• db, err := ksqlserver.New(ctx, connURL, ksql.Config{})
• db, err := ksqlite3.New(ctx, connURL, ksql.Config{})

Another reason this was done in separated packages is that we will be able to create submodules for each of these in the future,
meaning that if the user imports one of these he will load only the dependencies of this package and not the dependencies used for
connecting with other database technologies.

This release also deprecates the NewWithPGx() constructor.

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This discussion was created from the release Create Better Encapsulated Constructors for each Database.