[postgres] Reimplement PostgresDriver using deno-postgres

[uki00a]

https://github.com/denolib/typeorm/runs/928947102

Tasks

• Add basic implementation (feat: basic implementation for PostgresDriver #20)

• Enable PostgresDriver in CI (49abf4d)

• Implement missing features and fix failing tests

  • Add support for cube
    • https://github.com/denolib/typeorm/blob/master/test/functional/cube/postgres/cube-postgres.ts
  • Add support for enum array
    • https://github.com/denolib/typeorm/blob/master/test/functional/database-schema/enums-array/enums-array.ts
  • Add support for array types (may be resolved at fix: support deno@v1.2.0 #85)
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/1600/issue-1600.ts
  • Add support for enum types
    • https://github.com/denolib/typeorm/blob/master/test/functional/database-schema/column-types/postgres-enum/postgres-enum.ts
    • https://github.com/denolib/typeorm/blob/master/test/functional/database-schema/enums/enums.ts
    • https://github.com/denolib/typeorm/blob/master/test/functional/database-schema/simple-enums/enums.ts
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/1997/issue-1997.ts
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/2871/issue-2871.ts
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/4106/issue-4106.ts
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/4630/issue-4630.ts
  • Add support for hstore
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/922/issue-922.ts
    • https://github.com/denolib/typeorm/blob/master/test/github-issues/4719/issue-4719.ts
  • Fix increment issue
    • https://github.com/denolib/typeorm/blob/master/test/other-issues/ekifox-increment-issue/ekifox-increment-issue.ts
  • Improve compatibility with the original typeorm (update: bump deno-postgres to v0.4.1 #57)

• typeorm/src/driver/postgres/PostgresQueryRunner.ts

  Lines 210 to 219 in 49abf4d

  	// TODO(uki00a) We want to preserve the same behavior as node-postgres.
  	// switch (result.command) {
  	// case "DELETE":
  	// case "UPDATE":
  	// // for UPDATE and DELETE query additionally return number of affected rows
  	// ok([result.rows, result.rowCount]);
  	// break;
  	// default:
  	// ok(result.rows);
  	// }

[u-ways]

Hello, can you add the hacktoberfest label please?