Cherry-pick branch 'jorgen.lind/gcp_empty_chunks' into 'release/0.12'

See merge request !117

build: fix compilation on Windows

See merge request !92

The utility::string_t used by the AzureStorage backend is a typedef
for std::wstring defined in cpprestsdk:
https://github.com/microsoft/cpprestsdk/blob/master/Release/include/cpprest/details/basic_types.h#L36
On Windows std::wstring is a 2 byte wide utf16 character stream. To
securly convert between std::wstring and std::string on Windows a utf16
-> utf8 routine has be applied. Also there are no implecit conversions
from std::wstring and std::string.

chore: clean up, refactor, reorganize, improve

See merge request !100

docs: 📝 the main README.md has been reviewed and fixed

See merge request !97

ci: add sanitizer testing

See merge request !99

fix: race conditions

See merge request !98

fix: azure-curl provider exception type leaks to through core apis to customer!

See merge request !94

build: various build fixes ( libxml2  > 2.9.10 ), gcp provider after new logging...

See merge request !91

build: automate build for ftest, remove redundant coding

See merge request !96

fix: ftest/rtest Windows build

See merge request !95

feat: add user-specified HTTP headers to ss svc requests

See merge request !93

Add multi-level logging (AWS)

See merge request !90

Add multi-level logging (IBM)

See merge request !89

Dockerfiles: semicolon ignores errors

See merge request !85

Add multi-level logging

See merge request !88

ci: updating abi-check script

See merge request !87

fix: restore AWS storage console output

See merge request !86

ci: publish abi results

See merge request !83

ci: add Clang sanitizers to build scripts and Docker images

See merge request !82

ci: fix scan for secrets

See merge request !81