[clang-tools-extra] [clang-tidy] Add a new check 'performance-string-view-conversions' (PR #174288)

[Zinovy Nis via cfe-commits]

irishrover wrote:

> lgtm, one nit

Thanks for all your patience with this PR) 
Is it Ok to merge or should I wait for one more reviewer, for example EugeneZelenko?

https://github.com/llvm/llvm-project/pull/174288