Let every table have a primary key for MySQL

[hpoettker]

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Resolves #4146.

The PR sets a primary key for every table of the Spring Batch schema for MySQL.

Currently, the table BATCH_JOB_EXECUTION_PARAMS has no unique key. With MySQL, this has disadvantages in replication setups typically used in production: For example, it can cause performance problems with row-based replication, prohibits the use of parts of the Percona Toolkit, and limits the use of Galera cluster.

Setting not only unique keys but primary keys has additional advantages. In particular, sql_require_primary_key can be set to ON.