[clang][deps] Print timing information

This patch adds new `-print-timing` option to `clang-scan-deps`. It measures the wall and process time taken to scan dependencies for the compilation database. This provides more representative data compared to measuring the timing for the whole tool invocation, since that includes parsing and generating JSON files, which can be significant for larger inputs.

Reviewed By: akyrtzi

Differential Revision: https://reviews.llvm.org/D147815