[sanitizer_symbolizer] RenderContextual elements for symbolizer markup.

This is part of a stack of PRs to add support for symbolizer
markup in linux.

Render contextual symbolizer markup elements. For Fuchsia it is not
necessary to emit any context given that Fuchsia's logging
infrastructure already handles emitting it when necessary.

For more information about contextual symbolizer markup elements:
https://llvm.org/docs/SymbolizerMarkupFormat.html#contextual-elements

Reviewers: PiJoules, petrhosek, vitalybuka

Reviewed By: petrhosek, vitalybuka

Pull Request: https://github.com/llvm/llvm-project/pull/73194