Parser: Add identity column parsing

[KieranKaelin]

Dependent on #58 and #62.

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Oracle tables frequently contain IDENTITY columns, a popular feature used to implicitly create and use sequences.

Goal

The parse_table function shall understand identity columns and produce an appropriate AST.
As all sequence related syntax is shared with parse_sequence, there shall be no code duplication.

Examples

CREATE TABLE "HR"."TABLE_WITH_IDENTITY_ALWAYS"("ID" NUMBER(10,0) GENERATED ALWAYS AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOKEEP  NOSCALE);

CREATE TABLE "HR"."TABLE_WITH_IDENTITY_BY_DEFAULT_ON_NULL"("ID" NUMBER(10,0) GENERATED BY DEFAULT ON NULL AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOKEEP  NOSCALE);

CREATE TABLE "HR"."TABLE_WITH_IDENTITY_BY_DEFAULT"("ID" NUMBER(10,0) GENERATED BY DEFAULT AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOKEEP  NOSCALE);

CREATE TABLE "HR"."TABLE_WITH_IDENTITY"("ID" NUMBER(10,0) GENERATED ALWAYS AS IDENTITY MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 1 START WITH 1 CACHE 20 NOORDER  NOCYCLE  NOKEEP  NOSCALE);

How to demo

Appropriate tests are created showcasing the resulting AST and AST accessors to iterate and inspect the table properties.