Add logging for parameters

[mirromutth]

Motivation:

See also #138 .

When driver executing a text statement (no binding), log will like:

2023-12-31 | 23:59:59.999 | reactor-tcp-nio-1    | DEBUG | i.a.r2dbc.mysql.QUERY | Executing statement [SELECT 1]

When user is using client-preparing statements, log will like:

2023-12-31 | 23:59:59.999 | reactor-tcp-nio-1    | DEBUG | i.a.r2dbc.mysql.QUERY | Executing statement [SELECT value FROM test WHERE id=?] with [1]

When user is using server-preparing statements, log will like:

2023-12-31 | 23:59:59.999 | reactor-tcp-nio-1    | DEBUG | i.a.r2dbc.mysql.QUERY | Executing statement [INSERT INTO test VALUES(DEFAULT,?)]
2023-12-31 | 23:59:59.999 | reactor-tcp-nio-1    | DEBUG | i.a.r2dbc.mysql.QUERY | Prepared statement 1 [INSERT INTO test VALUES(DEFAULT,?)]
2023-12-31 | 23:59:59.999 | reactor-tcp-nio-1    | DEBUG | i.a.r2dbc.mysql.QUERY | Executing prepared statement 1 with [10]

Modification:

• Makes all implementation of AbstractMySqlParameter need to override toString.
• Add some descriptions of statements logging in README

Result:

More human-friendly SQL debugging logging.

[jchrys]

LGTM

However, I'm concerned about the breaking change(*MySqlParameter#toString exposes its value, Debug level Query Logger exposes params). Suggest merging with the next minor version update or log with params only when trace level is enabled. Let's discuss before merging.

[mirromutth]

I fixed a little miss in the README, and I added an override of toString() in the example of MySqlParameter.

[JohnNiang]

LGTM