Release/25.3 (#21195)

* Bump version number

* Update draft release notes for 25.3.

* Update draft release notes for Jetpack 25.3.

* Release Notes: add new section for next version (25.4)

* Add 25.3 release notes

* Freeze strings for translation

* Merge 25.3 editorialized release notes to release/25.3 (#21142)

* Update WordPress `PlayStoreStrings.po` for version 25.3

* Update Jetpack `PlayStoreStrings.po` for version 25.3

---------

Co-authored-by: Automattic Release Bot <[email protected]>