Bump mono - master ([master] Bump msbuild to track xplat-master #18372)

Enable roslyn maestro subscription for master ([mono] Update from upstream+mono-2019-10 msbuild#212)

Try enabling subscriptions for 2019-10

websdk subscription is missing from toolset. Figure out which channel to use for this

Some subscriptions are on release channel. Need to mirror what toolset has

Add coherent-parent dependencies - this will remove the mirroring requirement([mono] Add CoherentParent dependencies to stay in sync with dotnet/toolset msbuild#170)

Test subscription updates

Roslyn updates, eng/Packages.props won't be updated by maestro? Maybe use manual merge policy for this ([mono] Allow roslyn+nuget updates from maestro msbuild#181)

NuGet.Build.Tasks versions need to be updated in eng/Packages.props too

Add subscription for xplat-master