Use database helpers to create partitioned tables

What does this MR do and why?

It turns out that it is possible to use the options: attribute on create_table to append partitioning arguments for the table creation. This MR updates the current docs to make table creation easier.

Screenshots or screen recordings

[1] pry(main)>     Ci::Build.connection.create_table(:p_ci_examples, primary_key: [:id, :partition_id], options: 'PARTITION BY LIST (partition_id)', if_not_exists: true) do |t|
      t.bigserial :id, null: false
      t.bigint :partition_id, null: false
      t.bigint :build_id, null: false
[1] pry(main)> Ci::Build.connection.create_table(:p_ci_examples, primary_key: [:id, :partition_id], options: 'PARTITION BY LIST (partition_id)', if_not_exists: true) do |t|
  t.bigserial :id, null: false
  t.bigint :partition_id, null: false
  t.bigint :build_id, null: false
   (3.6ms)  CREATE TABLE IF NOT EXISTS "p_ci_examples" ("id" bigserial NOT NULL, "partition_id" bigint NOT NULL, "build_id" bigint NOT NULL, PRIMARY KEY ("id", "partition_id")) PARTITION BY LIST (partition_id) /*application:console,db_config_name:ci,console_hostname:rocket-sled.local,console_username:marius,line:(pry):1:in `__pry__'*/
=> #<PG::Result:0x00000001378ce230 status=PGRES_COMMAND_OK ntuples=0 nfields=0 cmd_tuples=0>

gitlabhq_development_ci=# \d+ p_ci_examples
                                            Partitioned table "public.p_ci_examples"
    Column    |  Type  | Collation | Nullable |                  Default                  | Storage | Stats target | Description
--------------+--------+-----------+----------+-------------------------------------------+---------+--------------+-------------
 id           | bigint |           | not null | nextval('p_ci_examples_id_seq'::regclass) | plain   |              |
 partition_id | bigint |           | not null |                                           | plain   |              |
 build_id     | bigint |           | not null |                                           | plain   |              |
Partition key: LIST (partition_id)
Indexes:
    "p_ci_examples_pkey" PRIMARY KEY, btree (id, partition_id)
Number of partitions: 0

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