[Release 1.1] Update release notes for v1.1.2 (dotnet#526)

Update release notes for 2.0.0-preview2 version (dotnet#486)

* Release notes for 2.0.0-preview2 version

* Apply suggestions from code review

Co-Authored-By: David Engel <[email protected]>
Co-Authored-By: Karina Zhou <[email protected]>

Co-authored-by: David Engel <[email protected]>
Co-authored-by: Karina Zhou <[email protected]>

[Release 1.1] Update Release notes for v1.1.1 (dotnet#430)

Release notes for Preview release v2.0.0-preview1 (dotnet#392)

Release Notes for Microsoft.Data.SqlClient 1.1.0 GA (dotnet#320)

Release notes for AKV Provider 1.0.0 GA (dotnet#318)

Release notes for 1.1.0 preview 2 (dotnet#297)

Release notes for AKV Provider 1.0.0-preview1.19295.2.

Add Release Notes for Azure Key Vault provider 1.0 (dotnet#278)