v5: fix(postgres): parse enums correctly when describing a table

[closingin]

This PR is a cherry-pick of #12409, as the bug exists in v5 and v6!

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• Does npm run test or npm run test-DIALECT pass with this change (including linting)?
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Description of change

When you have a PostgreSQL table containing a user-defined enum, if the last value of this enum contains multiple words, using a describeTable() on it will generate an array with a trailing quote due to a bad parsing of the result data. It works well in other cases (as long as the enum doesn't end with a multi-word value).

Consider this schema:

CREATE TYPE my_enum AS ENUM ('foo', 'bar', 'foo bar');
CREATE TABLE my_table (
  foo my_enum
);

Sequelize uses array_agg(pg_catalog.pg_enum.enumlabel) to fetch the enum values, before passing it to QueryGenerator.fromArray() to parse it. In this case it will send the string {foo,bar,"foo bar"}, and the resulting array will be ['foo', 'bar', 'foo bar"'], with the unwanted trailing quote.

---

Tests aren't passing but I'm not sure that it's related to my fix, tell me if I need to change something! Here's the stacktrace just in case:

> mocha --require scripts/mocha-bootload --globals setImmediate,clearImmediate --exit --check-leaks --colors -t 30000 --reporter spec "test/integration/**/*.test.js"

FIXME: I want to be supported in this dialect as well :-(


  [POSTGRES] Alias
    1) "before each" hook for "should uppercase the first letter in alias getter, but not in eager loading"


  0 passing (1m)
  1 failing

  1) "before each" hook for "should uppercase the first letter in alias getter, but not in eager loading":
     Error: Timeout of 60000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.
      at listOnTimeout (internal/timers.js:549:17)
      at processTimers (internal/timers.js:492:7)

[sushantdhiman]

🎉 This PR is included in version 5.22.0 🎉

The release is available on:

• npm package (@v5 dist-tag)
• GitHub release

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