Add a way to build the Tier 2 interpreter on Windows

[gvanrossum]

Feature or enhancement

Once gh-118339 lands the Windows build has only two options when it comes to JIT/Tier 2:

• Default build has no JIT and no Tier 2 interpreter
• Building with PCbuild\build.bat -enable-jit builds the JIT and enables it by default

We've added fancy options to --enable-experimental-jit for Unix builds; we should offer the same options for Windows (see gh-118335).

The idea is that you can specify independently:

• Whether to build the JIT, the Tier 2 interpreter, or neither (both is not an option)
• Whether it's enabled by default at runtime (if built at all), overridable by PYTHON_JIT=0|1 environment variable (see Python/pylifecycle.c).

The C code expects the following:

• _Py_TIER2 is set when building with JIT or with Tier 2 interpreter
• _Py_JIT is set when building with JIT

[brandtbucher]

This is done, right?