Prepare for September release

[Patater]

Description of defect

Mbed OS is not yet ready for a September release. We need to perform a few tasks to prepare.

Must

• Investigate and fix heap allocation test failure with GNU Arm Embedded Toolchain 10.3-2021.07 #15023
• Upgrade our testing systems to use GNU Arm Embedded Toolchain 10.3-2021.07 as the new supported version of gcc #14968
• Upgrade our testing systems to use Arm Compiler 6.16 as the new supported version of armclang #14969
• Issue with SFDP parsing of the Sector Map Parameter Table #12574
• Upgrade to TF-M v1.4 #14977

Should

• Rework SFDP/BlockDevice to support region overlap #15048
• Upgrade Mbed TLS to 3.0.0 to align with the version shipped by TF-M v1.4.0 #15049
• Drop Python 2.7 support #14784
• Move unsupported features under the "experimental" flag #14984
• Deprecate device management in mbed-cli1 (=legacy) #15009

Target(s) affected by this defect ?

All

Toolchain(s) (name and version) displaying this defect ?

GCC and Armclang

What version of Mbed-os are you using (tag or sha) ?

mbed-os-6.13.0

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

Mbed CLI 2

How is this defect reproduced ?

• Attempt to use newer version of GCC or Arm Compiler and find bugs that we could have caught and resolved by testing these toolchains in our CI.
• Attempt to use QSPIFBlockDevice with CYW9P62S1_43012EVB_01 and run into issues described in Issue with SFDP parsing of the Sector Map Parameter Table #12574

[Patater]

September release is out. We did the "Must" items but not the "Should" items.