Give the app space to grow in internal KVStore default configuration

[davidsaada]

Description

Prior to this change, the space left for the internal TDBStore (when working in the default internal configuration) was allocated from the sector following the end of the application until the end of flash. While this worked, it was problematic if the application would have crossed the sector boundary after an update. This PR leaves the application a couple of sectors to grow at the expense of the allocated storage (if they are available, which is the likely case).

This PR is defined as a breaking change, even if not a typical one: Boards that use the default internal configuration will lose the storage content after the upgrade (as the internal storage start will move forwards). Two boards will be affected: K66F and FUTURE_SEQUANA_M0_PSA. Non default configurations won't be harmed.

Pull request type

[ ] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[x] Breaking change

[davidsaada]

Rebased. No longer depending on anything.

[cmonr]

@davidsaada Thank you for the description on why this would be considered a breaking change.

Is it possible that maaybe the default configurations themselves should also be changed/updated?

Fyi @ARMmbed/team-nxp @lrusinowicz

[davidsaada]

@cmonr Default configurations by nature only include a minimal set of parameters, allowing the code to calculate the storage parameters automatically. The thing that was changed here was the way it's calculated in the internal flash case. Therefore, it seems that we don't need to change anything else. I also guess that many users would choose to tweak the storage parameters (start address, size etc.), which won't be affected by this change.

[0xc0170]

Updated, needs reviewers !

[davidsaada]

Closing this PR as apparently its code was added to #9237 (thought it had depended on this PR, appears that code was copied there).