Rewrite and bugfix no-switch-case-fallthrough

[ajafff]

PR checklist

• Fixes: switch-case-fall-through check failed on blocked case clauses #785, no-switch-case-fall-through does not detect conditionals #950, no-switch-case-fall-through: Expect break before default #1033, no-switch-case-fall-through thrown on nested switch statements where all cases of inner switch have return statements #1538
• New feature, bugfix, or enhancement
  • Includes tests

What changes did you make?

[bugfix] handle break, throw, continue and return nested in block, if-else and switch
[bugfix] allow empty case clauses before default clause
[enhancement] allow single line comment // falls through

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

Depends on #2217

[nchen63]

@ajafff thanks!

[ajafff]

Github didn't automatically closed the other open issues mentioned above: #950, #1033, #1538

[glen-84]

The // falls through comment check should probably be case-insensitive and allow additional text.

• // falls through
• // Falls through
• // Falls through.
• // Falls through -- for reasons.

[ajafff]

@glen-84 makes sense. I opened #2983 to address this.