Rewrite no-unused-expression and remove no-unused-new

[ajafff]

PR checklist

• Addresses an existing issue: Deprecate no-unused-new #2244
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

[removed-rule] no-unused-new removed, with logic moved into no-unused-expression
[new-rule-option] no-unused-expression adds option allow-new to allow new without using the new object
[new-rule-option] no-unused-expression adds option allow-tagged-template to allow tagged templates for side effects
Fixes #2293
[bugfix] no-unused-expression allow comma separated assignments
Fixes: #2058
[enhancement] no-unused-expression allow indirect eval (0, eval)("");
[enhancement] no-unused-expression checking for unused new can now use option allow-fast-null-checks
Fixes: #1839
[enhancement] no-unused-expression find unused comma separated expressions in all locations of the code
[enhancement] no-unused-expression find unused expressions inside void expression

Is there anything you'd like reviewers to focus on?

As @andy-hanson mentioned in #2244 no-unused-new is not worth its own rule. This PR integrates it in no-unused-expression and removes the rule.

[ajafff]

I added special handling for tagged templates to fix #2293 behind a new config option to explicitly allow them. For me that was the best way to go as I don't want to encourage anyone to use tag functions for side effects. That's just my opinion. I can still remove the option and make it the default.

no-unused-new is now completely removed. Let me know if we need a temporary solution to deprecate it properly

[adidahiya]

For me that was the best way to go as I don't want to encourage anyone to use tag functions for side effects. That's just my opinion.

I agree, sgtm

no-unused-new is now completely removed. Let me know if we need a temporary solution to deprecate it properly

Nah, I think this is fine since it's going into 5.0

[nchen63]

lgtm