Fix memory leak in aws_tls_connection_options_copy (awslabs#475)

Issue:
Memory leak in Connection function is reported at aws/aws-iot-device-sdk-cpp-v2#215
We tracked down the issue and find it is related to aws_tls_connection_options_copy.

Description of changes:
Release the tls option data before copy happens in aws_tls_connection_options_copy.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Fix aws-crt-swift by moving PKCS#11 headers (awslabs#473)

**Issue:**
aws-crt-swift is breaking when Swift tries to compile the official PKCS#11 headers.

These headers weird and need a bunch of things `#defined` before they're `#included`. Seems like Swift is trying to compile/parse each individual header under `include/...`, even if we add these files to the [exclude](https://developer.apple.com/documentation/swift_packages/target/2880334-exclude) list

**Description of changes:**
Move official PKCS#11 headers (and all files that include them) out from under the `include/...` folder.

Extend badssl-based tls testing (awslabs#414)

* Extend badssl-based tls testing

Remove platform ifdefs from tls_channel_handler.h (awslabs#460)

**Issue**
It was annoying and error prone having to mirror these ifdefs around every function that could call these functions, and every function that could call those functions, etc, etc, etc. There were multiple compilation errors in aws-crt-cpp on iOS because we didn't exactly match the nested pattern of ifdefs previously seen here.

**Description of changes:**
Instead of ifdef-ing out platform-specific functions in the H file, just ifdef in the C file, and raise a runtime error on unsupported platforms.

Fix null-pointer crash when s2n_connection_new() fails (awslabs#457)

Fix bug introduced in [PR awslabs#451](awslabs#451) and released in v0.10.13.

const pointer (awslabs#456)

Support PKCS#11 for mutual TLS on Unix platforms (awslabs#451)

Merging the `pkcs11` feature branch to `main`. Previous Pull Requests can be found here:

- awslabs#410 - Add PKCS#11 headers
- awslabs#408 - Public API first pass
- awslabs#412 - Implement library load/unload
- awslabs#413 - Get tests running in CI
- awslabs#425 - Find private key / begin s2n integration
- awslabs#428 - Finish integration with s2n
- awslabs#430 - Add tests. Each test now sets up its own tokendir.
- awslabs#431 - Misc fixes
- awslabs#432 - Add TLS test
- awslabs#434 - Handle connection failure during PKCS#11 operations
- awslabs#439 - Support multiple digest types for RSA
- awslabs#440 - Misc fixes
- awslabs#445 - Each CKR_ return value has its own AWS error-code
- awslabs#443 - Add license for PKCS#11 headers
- awslabs#442 - Behavior enum controls how C_Initialize() and C_Finalize() are called.
- awslabs#450 - Misc fixes

Co-authored-by: Prateek Yadav <[email protected]>

Moved aws_path_exist checks over to the safe variant. (awslabs#448)

Add Round 3 Cipher Pref List to Allowlist (awslabs#447)

Replace tls double channel (awslabs#441)

* Remove test first
* Add codebuild job spec that will run downstream integration tests (aws-c-http) that exercise double tls
* Add channel API to read from initial handler