Upgrade from .Net 6 to .Net 8

[henriqueholtz]

• Updated all projects from .Net 6 to .Net 8
• Updated All Nuget Packages to the latest version, except:
  • SixLabors.ImageSharp: breaking changes
  • MailKit: breaking changes
  • FluentValidation: breaking changes
  • Rollbat and Rollbar.NetCore.AspNet: breaking changes
• Removed deprecated package (AutoMapper.Extensions.Microsoft.DependencyInjection)
• Updated Dockerfile
• Updated Github Actions

[AppVeyorBot]

:x: Build Sharebook-Backend: PR Check 1.0.90-auqygqph failed (commit https://github.com/SharebookBR/sharebook-backend/commit/c3d39879e5 by @henriqueholtz)

[AppVeyorBot]

:x: Build Sharebook-Backend: PR Check 1.0.90-nqlkpeew failed (commit https://github.com/SharebookBR/sharebook-backend/commit/3dfa2669bc by @henriqueholtz)

[AppVeyorBot]

:x: Build Sharebook-Backend: PR Check 1.0.90-ohvjwtqb failed (commit https://github.com/SharebookBR/sharebook-backend/commit/0ed3c83363 by @henriqueholtz)