[roll] Roll fuchsia [bazel_sdk] Change how common definitions are shared between workspaces.

This is the second CL in a series that refactors how the shared
definitions of the Bazel SDK rules and in-tree workspace are used.

This CL changes how `//build/bazel_sdk/bazel_rules_fuchsia/common`
is exposed to the SDK and in-tree Bazel workspaces. This is done to
simplify fuchsia_clang_repository() which can now only create a
single top-level `common` symlink to that directory, as the whole
content under it can be used safely now.

To do so, a new convention is enforced, where any external repository
which wants to use these shared definitions should reference them
through a top-level `common` package/directory.

For `@fuchsia_sdk//common`, this is already the case, as this maps
directly to `//build/bazel_sdk/bazel_rules_fuchsia/common` by
construction.

For `@fuchsia_clang//common`, this is done by creating a simple
symlinks to the same location, which simplifies the
`fuchsia_clang_repository()` rule, which no longer needs to keep
track of the exact set of files to symlink.

For `@fuchsia_sdk_common`, which is only used by the in-tree
build (and the Bazel SDK test suite which runs in-tree), a new
`build/bazel/local_repositories/fuchsia_sdk_common` directory
is created with a single `common` symlink as well.

This setup allows removing the `common_package_prefix` argument
introduced in a previous CL, as now all functions defined in
the common area can assume they can reference other files from
the same set using `//common:<path>` or
`//common/<package>:<path>`.

This simplification will also allow moving more definitions
to the common area in the future. In particular those related
to C++ toolchain definitions.

Original-Bug: 366156651
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1120393
Original-Revision: 7a773525609b4427e4d664d53657db1a3778568f
GitOrigin-RevId: 86fa6176b59182eb4ac903c8f2db69614fe04dac
Change-Id: Ic8b7657fa017144f7c9a6ad5c49c42da20599f12