Documentation for performance is fragmented

[laurentlb]

The documentation about performance is in different places:

• https://docs.bazel.build/versions/master/guide.html#profiling
• https://docs.bazel.build/versions/master/skylark/performance.html (some of it doesn't seem specific to Starlark)
• https://docs.bazel.build/versions/master/memory-saving-mode.html

I think it would be useful to consolidate the information in one place.

This blog post may also contain information to put in the documentation: https://filipnikolovski.com/posts/bazel-performance-in-a-ci-environment

[jin]

There's also the Android specific page at https://docs.bazel.build/versions/master/android-build-performance.html