Docs: Abridged Reference: Operators / other operators and tokens

[BillWagner]

These don't fit any group, and should have a single page for each operator.

• ? : (conditional operator). Somehow, it feels out of tune with the logical operators.
• ?? (null coalescing). It also feels not in the logical operations group. Most probably, it's because I limit logical operations to those on bool operands.
• +, += (string concatenation and delegate combination)
• -, -= (delegate removal)
• :: (namespace alias qualifier)
• nameof
• sizeof
• await
• new operator
• stackalloc operator
• => (lambda declaration)

Sub-tasks are:

• [ ] Create the new articles
• [ ] Search for existing issues on content being migrated and consolidated. This is a good opportunity to fix those.
• [ ] Redirect existing content to the new articles.
• [ ] Remove old articles.
• [ ] Update all links in the .NET Content

[BillWagner]

Operators that were missing in the first review that should be added:

• new operator
• stackalloc operator

The description has been edited to reflect that.

[pkulikov]

@BillWagner to confirm: the listed operators should have a separate page for each of them.

Given that, I suggest (they are already merged in the list in the issue text) to merge pages for the + and += operators (- and -= pair as well) and put focus at these pages on the non-arithmetic behavior.

[BillWagner]

@pkulikov That would be perfect.

[pkulikov]

@BillWagner could you please assign this issue to me, as the half of it is already done.

The remaining operators to revise and move to the operators' TOC:

• [x] :: (namespace alias qualifier)
• [x] nameof
• [x] sizeof
• [ ] await
• [x] new operator

Not in the original list, but should the following two also be included?

• [x] default
• [x] delegate