feat: Update migrations postgres URI parsing and add tests

[fbis251]

This PR updates the parsing and formatting of the URI that is used when applying migrations and adds tests for sample input connStrings

As of 94d7d68539b6980cece521b428733f6c344bc268, using a connString with a non-default port number will ignore the custom port and default to 5432 in PgBackend.initializeDB when attempting to run migrations. The current connString formatting code will read pgxCfg.Host but not pgxCfg.Port when generating the new connString

• postgresq://localhost:5433/neoq?sslmode=disable - Example input connString
• postgresq://localhost/neoq?sslmode=disable&x-migrations-table=neoq_schema_migrations - connString that is actually used by PgBackend to try to apply migrations, note the default 5432 port number will be used since it's not specified

https://github.com/acaloiaro/neoq/blob/94d7d68539b6980cece521b428733f6c344bc268/backends/postgres/postgres_backend.go#L356-L361

Note that pq-style URLs are not supported, please let me know if you would like support for them

[acaloiaro]

Hi @fbis251 -- are you still interested in moving this PR forward?

[fbis251]

@acaloiaro I squashed, rebased against main, and updated the PR title to add the feat: prefix

[acaloiaro]

@fbis251 shippin' dreams, thanks again.