Update AdaptiveCards

[krschau]

Summary of the pull request

Update AdaptiveCards rendering, object model, and templating.

• Use svg string directly instead of converting it to base64 in widget charts (enabled by Add support for svg xml in the data scheme for images AdaptiveCards#8880)
• Use string-based templating APIs instead of Newtonsoft (enabled by Make AdaptiveCards.Templating AOT compatible AdaptiveCards#8919).
• Remove last remaining references to Newtonsoft
• In widget template, use ColumnSet's horizontalAlignment instead of empty column workaround (enabled by Added horizontal alignment AdaptiveCards#8936)

References and relevant issues

Detailed description of the pull request / Additional comments

Validation steps performed

PR checklist

• Closes #xxx
• Tests added/passed
• Documentation updated