[azure-core-cpp] Update to 1.6.0 (#24567)

## 1.6.0 (2022-05-05)

### Features Added

- Add `Azure::Core::Http::Request` constructor overload to support payload and non-buffered response.

### Bugs Fixed

- [[#3537]](https://github.com/Azure/azure-sdk-for-cpp/issues/3537) Updated field type `CurlTransportOptions.Proxy` from `std::string` to `Azure::Nullable<std::string>`. This allows libcurl to ignore the proxy settings from the environment when the string is empty.
- [[#3548]](https://github.com/Azure/azure-sdk-for-cpp/issues/3548), [[#1098]](https://github.com/Azure/azure-sdk-for-cpp/issues/1098) Improve performance of the Http transport on Windows by reusing the same session handle across all requests.

### Other Changes

- [[#3581]](https://github.com/Azure/azure-sdk-for-cpp/issues/3581) Update log level in retry policy from warning to informational.

ports/azure-core-cpp/portfile.cmake

@@ -1,8 +1,8 @@
 vcpkg_from_github(
     OUT_SOURCE_PATH SOURCE_PATH
     REPO Azure/azure-sdk-for-cpp
-    REF azure-core_1.5.0
-    SHA512 7a0b8ed9345b565e4476cb66c1e7a44350f5cd4f79a9d40a11b77f646eff353d94762803ca5931264689d390255cd9d361c5d4a54ccc89548cf640f76a26e74c
+    REF azure-core_1.6.0
+    SHA512 13374ddf74488c080ef19d78569961dc859cd95cb64f359e0d3a0d763a314f005a6ba51b8f8fe900a7acb3eb4b783f4570962569855f6e4839b02de4db0d026e
 )
 
 vcpkg_check_features(

ports/azure-core-cpp/vcpkg.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-core-cpp",
-  "version-semver": "1.5.0",
+  "version-semver": "1.6.0",
   "description": [
     "Microsoft Azure Core SDK for C++",
     "This library provides shared primitives, abstractions, and helpers for modern Azure SDK client libraries written in the C++."

versions/a-/azure-core-cpp.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "5b920c224b5fa4daa427701a123bdf213dac8c43",
+      "version-semver": "1.6.0",
+      "port-version": 0
+    },
     {
       "git-tree": "8940f6b17c33b8076e08c931fcf2ccdafa2fe2f2",
       "version-semver": "1.5.0",

versions/baseline.json

@@ -317,7 +317,7 @@
       "port-version": 3
     },
     "azure-core-cpp": {
-      "baseline": "1.5.0",
+      "baseline": "1.6.0",
       "port-version": 0
     },
     "azure-identity-cpp": {