[Pg] Add Temporal mapping support

[XiNiHa]

Related: #1776

• Mostly followed the opinions and approaches of jiff (Temporal-like datetime library in Rust) integration for sqlx: Support jiff as a date time lib backend launchbadge/sqlx#3487
  • timestamp => PlainDateTime
  • timestamptz => Instant
  • date => PlainDate
  • time => PlainTime
  • interval => Duration
• I've considered vendoring the postgres-interval dependency, but I'm not sure about the license issues. Some help would be appreciated.
• I don't know what ColumnDataType is used for, therefore I didn't add any Temporal types there and just used 'date's. Let me know if it should be added.
• I vendored the type definitions for Temporal from its reference polyfill, but it should be replaced with Add Temporal (Stage 3) types microsoft/TypeScript#60164 later.

[dahlia]

@XiNiHa Hey! This PR has conflicts now. 😅 Could you rebase when you get a chance?

The maintainers have been silent, but maybe resolving conflicts will help get their attention!

[XiNiHa]

Sure! I'll make it done until tomorrow 😋

[SamPearlma]

I picked this up and rebased it onto the latest main.

I also added test coverage, wired in the Temporal polyfill for Vitest, and adjusted the interval handling (removed the fallback due to unsafe parsing behavior with certain PostgreSQL interval formats).

New PR here for continuation/review:
#5656

@dahlia