* Fix warning on clang version 10.0.0-4ubuntu1
The warning was
```shell
../src/vcpkg/commands.porthistory.cpp:55:14: error: unused function 'is_date' [-Werror,-Wunused-function]
```
* Add environment variable VCPKG_USE_NUGET_CACHE
As the name suggests, this environment variable allow tu use Nuget
cache for Nuget binary caching sources.
* Document NuGet's Cache environment variable
* [vcpkg] Add experimental x-azblob binary provider
* [vcpkg] Test azblob storage provider in CI
* [vcpkg] Address some CR comments from #13639
* [vcpkg] Fixup azure-pipelines
* [vcpkg] Fix regression where the downloaded package is purged before decompressing
* [vcpkg] Further refactor vcpkg::Downloads
* [vcpkg] Enable OSX for x-azblob testing
* [vcpkg] Reduce diff against master
* [vcpkg] Extract Downloads::details::split_uri_view
* [vcpkg] Address PR comments
* [vcpkg] Add testing and metrics for x-azblob
* [vcpkg] Add docs for x-azblob
This includes a note that it is currently experimental
* [vcpkg] Address CR comments
* [vcpkg] Revert pipeline changes except OSX to minimize disruption
Co-authored-by: Robert Schumacher <roschuma@microsoft.com>
Co-authored-by: Billy Robert O'Neal III <bion@microsoft.com>
* [vcpkg_docs] Add note about GitHub hosted agents
* [vcpkg-docs] Add ./ prefixes to GitHub example
Co-authored-by: Robert Schumacher <roschuma@microsoft.com>
