idlelib/News3.txt for 3.14.0 and backports

[terryjreedy]

THIS ISSUE REMAINS OPEN FOR MORE PRS until 3.14.0 is released and News3.txt is updated to that release.
News items after the first are normally added issue by issue, but sometimes things happen.

Branch 'main' became 3.14.0a0 as of 3.13.0 beta 1: 2024-05-08
However, unless an patch was not backported to 3.13.b# or .rc#,
idlelib/News3.txt items continued going under
What's New in IDLE 3.13.0 on both main and 3.13, until 3.13.0, 2024-10-07
Subsequent news items go under
What's New in IDLE 3.14.0 (new header) on main branch
What's New in IDLE 3.13.z (new header) on 3.13 branch
What's New in IDLE 3.12.z (existing header) on 3.12 branch
In other words, idlelib News3.txt is handled as if main were branched off as of about 3.x.0rc?.
This is different from the changelog attached to What's New in 3.x.

Release peps -- needed for proposed and actual release dates.
3.12 PEP-693
3.13 PEP-719
3.14 PEP-664

Continues #112953

Linked PRs

• gh-129876: Initial 3.14 News3.txt entries #129881
• [3.13] gh-129876: Initial 3.14 News3.txt entries (GH-129881) #129882
• [3.12] gh-129876: Initial 3.14 News3.txt entries (GH-129881) #129883