rust: Add rust_bindgen std version w/ cc defaults.

Adds the c_std and cpp_std properties to rust_bindgen, and use the
default values from cc if these are undefined.

This assumes by default that the header extension indicates whether
the header is a C or C++ header file. This default can be overridden
by setting either c_std or cpp_std.

Test: Soong tests pass, "-std=" arg included in bindgen calls
Bug: 163580541
Change-Id: I5b0d3b8eae9a54dd91d8a0aca583d7803a344f27