IMDSv2 EC2 Metadata Client support and other improvements

Support IMDSv2 EC2 Metadata Client.

Basic IMDSv2 Client Implementation with an async API to acquire resource from EC2 Instance Metadata Service.

Provided high level APIs so you can easily access specific EC2 Metadata.

Refactored IMDS Credentials Provider, now most logic will be in IMDS Client.

Co-authored-by: Andrew Tang <tangliang551@gmail.com>

Old compiler fixes.

v0.3.15

Added newlines to some test files. (#82)

X509 proxy support

• Added proxy configuration to the x509 credentials provider

x509 credentials provider fix

• fixes an issue with the x509 credentials provider where the host header was not being sent

Support for additional credential providers, applied retry strategy to IMDS and STS, Rhel5 build fixes

Rhel5 build Fixes (#73)

* Rhel5 fixes

IMDS fixed to handle connection level shutdown errors. Also added secure IMDS provider. Updated to use latest http api.

Updated http calls, to use the new stream activate apis. Rewrote imds…

… creds provider state machinery (#66)

* Updated http calls, to use the new stream activate apis.
* Updated auth to use latest http api for read back pressure.
* Rewrote imds creds provider to handle closed connections and make a more flexible/maintainable state machine.

ECS credentials provider + fixes

• Add ECS credentials provider
• Hide CJSON symbols
• credentials provider testing framework fixes

Credentials expiration and time fixes

• Credentials expiration (#56)

• Properly use and separate high res and system time (#60)

Stats and other fixes

Stat (#29)

* Base statistics gathering and monitoring

Fix cmake config template, fix locking bug in tests.

Fixed cmake config template. (#53)

* Fixed cmake config template.

* uniitialized lock.