Standardize repository rule naming for 3rd party packages.

[sluongng]

I recently observe in https://github.com/aherrmann/rules_zig/ that the toolchain is managed via a rule called zig_repository, which follow the template convention of mylang_repository.

However, what I am used to in Go is go_repository is used to manage 3rd party dependency import. Toolchain in Go is managed via go_{download,local,host}_sdk and go_register_toolchains rules instead.

So I would suggest renaming mylang_repository to mylang_sdk and mylang_register_toolchains while reserving mylang_repository for respective language's 3rd party import. WDYT?