Remove support for webpack-dev-server v3 inside @cypress/webpack-dev-server

[AtofStryker]

What would you like?

With the next major version of Cypress, I would like to remove support for webpack-dev-server v3

Why is this needed?

webpack-dev-server v3 is now two major versions behind and hasn't been released in over 2 years 3.11.2. Removing the code from the @cypress/webpack-dev-server would lessen the burden of maintenance

Other

users would still be able to use CT with webpack-dev-server v3 support by using an older version of @cypress/webpack-dev-server. Support would no longer ship with Cypress by default