support TLS skip-verify

[csuzhangxc]

Feature Request

Is your feature request related to a problem? Please describe:

some MySQL servers may use a self-signed or invalid certificate, then in dumpling we may need skip-verify.

Describe the feature you'd like:

support specify to skip TLS verify.

Describe alternatives you've considered:

may we need to consider the server to verify the client?

Teachability, Documentation, Adoption, Optimization:

[dveeden]

Might be good to see if there are other TLS things that also need work, like requiring TLS. Setting a minimum TLS version is probably best done on the server instead.

Feel free to contact me if anyone wants to work on this and needs help.