Allow hyphens in machine name

Why?

I think hyphens(-) are not allowed in creation of table in most SQL. As we are using field machine name as table name so it will throw error in MySQL.

I think we can create table names with hyphen -in it but we have to enclose the table name in `. But why is it required we already have _.

Which machine names?

Some already allow hyphens, eg menu IDs

Each config entity can set its own rules.

Since there's been no follow up about "why" this is needed or specifically where I'm going to close out.