Added support for multiple oracle pools

[cemremengu]

This PR adds support for multiple pool definitions.

Changes

• Options now support a name property for pool labeling (note that this is not poolAlias). Labeled clients can be accessed via oracle.<dbname>.getConnection()
• oracledb instance is exposed as oracle.db so that you can access constants and other options such as constants like oracle.db.OBJECT
• (breaking) getConnection is preserved but the pool instance is now accessed via oracle.pool

fastify.register(require("fastify-oracle"), {
pool: {
  user: "oracle",
  password: "oracle",
  connectString: "oracle.local:1521/mydb"
},
name: 'mydb'
})

async function (request, reply) {
 // Or this.oracle.mydb.getConnection()
  const conn = await this.oracle.getConnection()
  try {
    const result = await conn.execute("SELECT 1 FROM DUAL",{ }, { outFormat:this.oracle.db.OBJECT })
    return result.rows
  } finally {
    await conn.close()
  }
}

fastify.register(require("fastify-oracle"), {
pool: {
  user: "oracle",
  password: "oracle",
  connectString: "oracle.local:1521/mydb"
},
name: 'mydb'
}).register(require("fastify-oracle"), {
pool: {
  user: "oracle",
  password: "oracle",
  connectString: "oracle.local:1521/mydb"
},
name: 'otherdb'
})

async function (request, reply) {
  const myConn = await this.oracle.mydb.getConnection()
  const otherConn= await this.oracle.otherdb.getConnection()

  try {
    const myResult = await myConn.execute("SELECT 1 FROM DUAL",{ },{ outFormat: this.oracle.db.OBJECT })
    const otherResult = await otherConn.execute("SELECT 1 FROM DUAL",{ },{ outFormat: this.oracle.db.OBJECT})

    return {myResult, otherResult}
  } finally {
    await myConn .close()
    await otherConn.close()
  }
}

[cemremengu]

This PR ~no longer introduces a breaking change. It~ preserves and extends the previous API by exposing getConnection() method and pool object as individual properties. However, if you are using pool directly in your code, you will need to do oracle.pool

[cemremengu]

After spamming you gazillion of times (hopefully you unfollowed this PR), I think I am done 😄

[jsumners]

I just haven't had time to review it again. I'll get to it.