Knex' default implementation of _setNullableState fails for tables in non-standard schemas

[OliverHenrichs]

Environment

Knex version: 3.1.0
Database + version: Mssql 2019-latest
OS: N/A

@smorey2

Bug

1. What I get:
   I have an MsSql-table 'primary_table' in a non-standard schema called 'testSchema'.
   The table has a non-nullable column 'id_not_nullable'.
   I execute await knex.schema.withSchema("testSchema").table(tableName, (table) => { table.setNullable('id_not_nullable'); }); and it fails.

2. What it should do:
   Above code removes the 'not_nullable'-flag in the table's column.

3. Error message:
   .setNullable: Column [id_not_nullable] does not exist in table [testSchema].[primary_table].

4. Reduced test code

const knex = require('knex')({
  client: 'mssql',
  connection: { // knex.js' mssql docker config
    user: 'sa',
    password: 'S0meVeryHardPassword',
    server: 'localhost',
    port: 21433,
    database: 'knex_test',
  }
});

const schemaName = "testSchema";
const tableName = "primary_table";

/**
 * Prior to running create schema "testSchema" in DB (Knex doesn't support this for mssql)
 * */
async function main() {
  try {
    await knex.schema.withSchema(schemaName).dropTable(tableName);
  } catch {
    // on first run this does not work because table does not exist.
  }
  await knex.schema.withSchema(schemaName).createTable(tableName, (table) => {
    table.integer('id_nullable').nullable();
    table.integer('id_not_nullable').notNull();
  });
  try {
    const builder = knex.schema.withSchema("testSchema").table(tableName, (table) => {
      table.setNullable('id_not_nullable');
    });
    const queries = await builder.generateDdlCommands();
    console.log(queries);
    await builder;
  } catch (e) {
    /**
     * The error will say:
     *        .setNullable: Column [id_not_nullable] does not exist in table [testSchema].[primary_table].
     *
     * SetNullable does not work because the schema is actually not used in the resulting sql.
     * @see tablecompiler.js -> _setNullableState, lin 318ff read:
     *
     *          return this.client
     *           .queryBuilder()
     *           .from(this.tableNameRaw)
     *           .columnInfo(column)
     *
     * It should be including `.withSchema(this.schemaNameRaw)`:
     *
     *          return this.client
     *           .queryBuilder()
     *           .withSchema(this.schemaNameRaw) // if schema is undefined, this does not hurt.
     *           .from(this.tableNameRaw)
     *           .columnInfo(column)
     *
     *  which works.
     *  I will add a PR that does exactly this. 
     *  Should also be a thing in all connections that do not implement their own _setNullableState
    */
    console.log(e);
  }
  return 0;
}

main();