Blazor common sample enhancements

[guardrex]

Over the last few preview releases, a number of great examples have been added to the text of the docs but not the common sample app.

• Provide a list of suggestions for sample enhancements to management. See update.
• Enhance the sample based on feedback. See update.
• Move in-text code examples that require highlighting into snippets and apply highlighting. See update.
• As a convention in Blazor docs, probably should describe the use of the this keyword in samples and examples. UPDATE: Moved to UE tracking issue.
• This issue will likely be worked when the Fundamentals node Overview topic is added, and the snippet sample apps will get cross-linked into a section of the new topic with guidance on how to obtain them locally. A few devs do want to get the full code of our doc examples in one shot as opposed to cut-'n-paste of individual full-working snippets from topics. Also, I'll confirm that snippet samples run, and I'll deal with mock-up code in some of the Razor components that was required to get the apps to compile in order to use them to show snippets in topics. These non-functional Razor components should be made functional, or these examples should be moved back into non-fully-working example code blocks in the topics. Update: This is TBD and tracked by the UE tracking issue.

Items:

• The project templates have stabilized on the project/solution name of BlazorSample. Conform spots where topics say BlazorApp to the convention. Done!
• Drop prior sample apps and any reference to them (note that most/all of the references have already been dropped on the UE passes as code was moved to the snippet sample apps). Done!