Conditionally define strcasecmp in implementation of http_requester to remove msvc warnings.

Adds a `Version/LDClientSDK_Version`method, which exposes the client's
version via function call.

In the previous way, it was a public static class member. This way, we
have a bit more encapsulation and can also expose it via C binding.

We use Boost.URL, which was introduced in 1.81. Updates the find_package to require this as minimum version.

Moves both hello apps into an examples directory.
Moves contract tests into a contract-tests directory. 
Updates the SDK contract tests README with content.

Co-authored-by: Casey Waldren <cwaldren@launchdarkly.com>

Adds missing `context` parameter to docs on `LDClientSDK_Identify`.

Introduces an `AllFlags` binding for C. 

The strategy chosen is to convert the `std::unordered_map` returned by
C++ AllFlags into an `LDValue`, because we already have bindings for
object iteration. Additionally, once we add serialization, this could be
easily dumped to JSON.

Minor changes:
- Add `enum/struct` prefix to some C enums/structs
- Renamed some `Ld` prefixes to `LD`

Renames create/destroy object/array iterators to use new/free naming.

…130)

🤖 I have created a release *beep* *boop*
---


<details><summary>launchdarkly-cpp-client: 0.2.0</summary>

##
[0.2.0](launchdarkly-cpp-client-v0.1.0...launchdarkly-cpp-client-v0.2.0)
(2023-05-31)


### Features

* add AllFlags C binding
([#128](#128))
([9aa0794](9aa0794))
* Add C bindings for data source status.
([#124](#124))
([d175abb](d175abb))
* Add c bindings for FlagNotifier.
([#119](#119))
([11a7f61](11a7f61))
* add Version method to obtain SDK version
([#122](#122))
([1003117](1003117))


### Dependencies

* The following workspace dependencies were updated
  * dependencies
    * launchdarkly-cpp-internal bumped from 0.1.0 to 0.1.1
    * launchdarkly-cpp-common bumped from 0.1.0 to 0.2.0
</details>

<details><summary>launchdarkly-cpp-common: 0.2.0</summary>

##
[0.2.0](launchdarkly-cpp-common-v0.1.0...launchdarkly-cpp-common-v0.2.0)
(2023-05-31)


### Features

* add AllFlags C binding
([#128](#128))
([9aa0794](9aa0794))
* Add C bindings for data source status.
([#124](#124))
([d175abb](d175abb))
* Add c bindings for FlagNotifier.
([#119](#119))
([11a7f61](11a7f61))
* Allow for easier creation of contexts from existing contexts.
([#130](#130))
([5e18616](5e18616))


### Bug Fixes

* rename C iterator bindings to follow new/free pattern
([#129](#129))
([24dff9a](24dff9a))
</details>

<details><summary>launchdarkly-cpp-internal: 0.1.1</summary>

### Dependencies

* The following workspace dependencies were updated
  * dependencies
    * launchdarkly-cpp-common bumped from 0.1.0 to 0.2.0
</details>

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>