Moves builder/shell_parser and into its own subpackage at builder/shell since it
has no dependencies other than the standard library. This will make it
much easier to vendor for downstream libraries, without pulling all the
dependencies of builder/.
Fixes#36154
Signed-off-by: Matt Rickard <mrick@google.com>
Upstream-commit: a634526d14639c6b98c509a069ef29e2b69c0ef0
Component: engine
3ea1f0df2c