Restructure lwipstack directory

[gpsimenos]

Summary of changes

mbed-os/features/lwipstack directory restructured according to the internal proposal.

• Public headers moved into mbed-os/connectivity/lwipstack/include/lwipstack folder
• Source moved into mbed-os/connectivity/lwipstack/source folder

This is one of a series of PRs aiming to clean up the mbed-os directory structure. The intention is to create a consistent tree among mbed components, following the below structure:

[component name]
├── mbed_lib.json                     // Each component comes with their own config that's appended to the App/System ├── config 
├── CMakeList.txt                     // This depends on the build system choices, part of another PREQ
├── README.md
├── include                           // The top-level include path
│   └── [component name]              // Public headers that can be accessed by the developers - `#include [component name]/*.h`
│       └── internal                  // Internal headers that implement or are included by a public header or are needed by other Mbed OS libraries - `#include [component name]/internal/*.h`
├── source                            // Source files and private headers, available only inside the component's source directory
└── tests
    ├── <framework>                   // <framework> test folder (for example CPPUTEST)
    │   └── <test suite one>          // Can be either source file or a directory
    ├── UNITTESTS                     // Unit tests (previously in UNITTESTS) folder using googletest framework (to be renamed to gtest at a later stage)
    │   └── <unit test suite one>     // Can be either source file or a directory
    └── TESTS                         // Greentea tests (previously in TESTS) folder (to be renamed to greentea at a later stage)
        └── <greentea test suite one> // Can be either source file or a directory
 
mbed-os
└── TESTS (to be renamed to greentea at a later stage)
    ├── integration   
    └── system

Impact of changes

None

Migration actions required

None

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Documentation

None

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Pull request type

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[X] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

• All unit tests build successfully
• All greentea tests build successfully
• All example applications in https://github.com/ARMmbed/mbed-os-example-tls build successfully

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Reviewers

@evedon
@ashok-rao
@LDong-Arm

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[ciarmcom]

@gpsimenos, thank you for your changes.
@ashok-rao @evedon @LDong-Arm @ARMmbed/mbed-os-maintainers please review.

[LDong-Arm]

I wonder if lwip and lwip-sys subdirectories should be moved into source. They are like internal libraries used by connectivity/lwipstack.

[gpsimenos]

I wonder if lwip and lwip-sys subdirectories should be moved into source. They are like internal libraries used by connectivity/lwipstack.

Good shout. Moved those into source.

[0xc0170]

Commit 63d1f77 should contain details from the PR description

Pull request has been modified.

[gpsimenos]

Rebased and reworded 63d1f77.

[LDong-Arm]

LGTM

[gpsimenos]

Reverted previous commit moving lwip libraries inside source because that causes problems with the build system. The libraries must remain where they are for now.

[gpsimenos]

Ping @0xc0170 @adbridge

[adbridge]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 6 of 6 test jobs passed
Build number : 1
Build artifacts