Move static utils to the static library

These classes used to live as a static utility in the
NetworkStack module, but that's not the right place for
them.

The point of this patch is to *not* require topics, as
any change in this space will very quickly spin out of
control and become unmanageable. As such, this starts
with creating equivalent classes in a single, easier to
manage change. Followup changes will migrate users of
the old classes to use these ones instead. Finally, the
old classes can be removed. This way, work can be
broken down into separate changes and be checked in
little by little, rather than one huge topic with many
changes doing everything in one go, which is unlikely
to be manageable.

There are no code changes from the originals, but a
number of reorganizations, most of them unavoidable.

• Vertical spacing (these classes fix it)
• Package names/imports are adjusted
• Added @hide on NetlinkMonitor
• Move all contents of RouteUtils to NetdUtils, because
  all methods depend on INetd, and some of the targets
  do not/cannot depend on netd-client
• Restrict the files used by the filegroup
  net-utils-framework-wifi-common-srcs, since that
  target does not necessarily provide all dependencies
  to all its users.
• Don't move NetworkMonitorUtils, since it depends on
  SdkLevel, and net-utils-framework-common-srcs is
  using **/*.java. It would have been possible to list
  explicitly all files actually necessary in this
  filegroup, but NetworkMonitorUtils is actually only
  used by the networking modules and not the framework.
  Eventually it should move but it doesn't have to
  be in this patch, which is complicated enough as
  it is.
• RouteUtils is now empty, because some new methods
  will be added to it soon and it is less expensive
  to keep it empty than to remove it now and add it
  again later.
• Merge NetdUtils, and unify the constants.
Some changes to satisfy checkstyle :
• Remove unused imports
• Reorder modifiers in InterfaceController
• Remove {} in IpNetworkMonitor
• Remove redundant public modifier in IpNetworkMonitor
• Add javadoc to a few methods
• Add whitespace around | in InterfaceParams
However, don't rename members in IpNeighborMonitor
like checkstyle would prefer because this would make
migration to this more involved.

Test: NetworkStaticLibsTests NetdStaticLibTests
Change-Id: I439121cba5d7ea95aa4d6c80ea25207c316880a0
diff --git a/staticlibs/client-libs/Android.bp b/staticlibs/client-libs/Android.bp
index 8c79d2a..5cc011e 100644
--- a/staticlibs/client-libs/Android.bp
+++ b/staticlibs/client-libs/Android.bp
@@ -16,6 +16,7 @@
         "//frameworks/base/services:__subpackages__",
         "//frameworks/base/packages:__subpackages__",
         "//frameworks/libs/net/client-libs/tests:__subpackages__",
+        "//frameworks/libs/net/common:__subpackages__",
     ],
     libs: ["androidx.annotation_annotation"],
     static_libs: [