On disk cache serialization (dotnet#6094)

### Context
BinaryFormater serialization of on-disk RAR cache is slow and unsecure. 
Related issue: dotnet#6057

### Changes Made
Serialization changed to use custom binary format by using existing `ITranslatable` 

### Testing
Unit testing
Manual testing
- Roslyn repo rebuild + incremental build

[vs16.9] NuGet Feed Update (dotnet#6136)

Co-authored-by: Matt Mitchell <[email protected]>
Co-authored-by: Ben Villalobos <[email protected]>

Loc updates (dotnet#6102)

Co-authored-by: Cristiano Suzuki <[email protected]>

Update dependencies from https://github.com/dotnet/arcade build 20201…

…130.3 (dotnet#5961)

[vs16.8] Update dependencies from dotnet/arcade

Final branding for 16.8.0 (dotnet#5805)

Merge pull request dotnet#5754 from dotnet-maestro-bot/merge/vs16.8-t…

…o-master

[automated] Merge branch 'vs16.8' => 'master'

Merge pull request dotnet#5613 from ostorc/rarAsService/node

This PR provides MSBuild necessary infrastructure to start up new RAR node and connect to it.

Implements dotnet#5555

Suggestion to parse solution when projects have similar names (dotnet…

…#5367)

Created a fix to detect collision caused by a unique project name's normalization, reported on issue dotnet#3019

Fixes dotnet#3019

Final branding for 16.8 (dotnet#5545)

Final branding_16.6 (dotnet#5273)