[clang-format] Add new option to add spaces around conditions

Summary:
This diff adds a new option SpacesAroundConditions that inserts spaces inside the braces for conditional statements.

Reviewers: klimek, owenpan, mitchell-stellar, MyDeveloperDay

Patch by: timwoj

Subscribers: rsmmr, cfe-commits

Tags: clang, clang-format

Differential Revision: https://reviews.llvm.org/D68346