Rename `@volar/server` package name and cli command

[johnsoncodehk]

As a part of refactor tasks, I'm planing rename @volar/server to @volar/vue-language-server, and change cli command from volar-server to vue-language-server.

Considering this has some impact on other IDE tools, I'll keep this issue for a while.

[williamboman]

Hey! I think it'd be neat if the old executable had remained (but been deprecated), to allow room for tooling to update without breaking!

[johnsoncodehk]

Hi @williamboman, due to pkg name have been changed, I think if we still keep volar-server bin file in @volar/vue-language-server will make some confusion, because we can't know it actually mean to @volar/server or @volar/vue-language-server.