Add QbeastTable.forTable method

[osopardo1]

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We are only able to load the QbeastTable from Path now.

import io.qbeast.spark.QbeastTable

val qbeastTable = QbeastTable.forPath(spark, "/path")

we should be able to load it also for table name:

import io.qbeast.spark.QbeastTable

val qbeastTable = QbeastTable.forTable(spark, "table_name")