Soong: Refactor the soong_ui arguments processing to be more like bazel.

Currently, the command line argments is being processed in multiple
places. In the main soong_ui arguments, there are several if statements
that checks if a specific argument was specified in order to execute
the requested operation. This does not scale well when adding or
removing a command in the near future. In order to support the build
commands (m, mma, etc...) from the envsetup.sh in soong_ui, a refactor
was required in order to add a command rather quickly and to have the
flexibiity to unit test the command. The soong_ui arguments format is
as follows:

soong_ui <command> [<arg 1> <arg 2> ... <arg n>]

The <command> is a specific operation to be executed. The arguments
after the command are processed by the command itself.

Below is the list of changes made in this commit:

 * Created a new command infrastructure that allows adding
   or deprecating a command easily.

 * Fixed a bug when running ./soong_ui.bash directly would cause
   a panic due to index being out of range for args list.

Bug: b/130049705
Test: Below is the list of testing done on this commit:
    * Ran lunch and verified that the output is the same as the the output
      without the modifications. lunch indirectly runs soong_ui passing
      in the --dumpvar-mode (to read makefile variables such as
      TARGET_PRODUCT) and --dumpvars-mode (to build the build cache).
    * Ran ./soong_ui.bash directly (with unsupported flags and no flags)
      and the proper message appeared that soong native UI is not yet
      available.
    * Ran m, mm, mmm, mma, mmma commands.
    * Ran the make installclean command:
         make -j80 TARGET_PRODUCT=aosp_arm64 TARGET_BUILD_VARIANT=eng dist DIST_DIR=/tmp/helloworld installclean
    * Ran ./out/soong_ui -j80 --make-mode PRODUCT-aosp_arm64-eng dist checkbuild tests

Change-Id: Iee4de7ec0fa4661206fda8ae1fe6fa4487d9bb22
Merged-In: Iee4de7ec0fa4661206fda8ae1fe6fa4487d9bb22