Draft: main/mbedtls: upgrade to 3.6.0 LTS

https://github.com/Mbed-TLS/mbedtls/releases/tag/v3.6.0

https://github.com/Mbed-TLS/mbedtls/blob/v3.6.0/BRANCHES.md

First just make the aport itself build, then bump dependants.

This is not a security upgrade since CVE-2024-28960 was addressed in the 2.28.8 security upgrade in !63152 (merged).