For the most part, this change implements the same encoding
for tuples that we use for dynamic. This means that interface
implementations and generic constraints are not covered, but
base types and type parameters are.

This change also doesn't have full tests for "long" tuples (nested tuple
transformations) or tuple types that can only be constructed in
metadata.

This moves the last custom MicroBuild step into the Roslyn repo.  This now gives us fully control over the binaries produced and their final locations in our source.  No need to coordinate changes to the official build with source changes / branches.

Moved a PROTOTYPE comment to issue #12431, and report an unimplemented
error message rather than crashing the compiler when switching on float, double,
or decimal.

This implements lowering and good code generation for typeswitch. However, if the switch can be
handled using the old strategy, we completely reuse the old binding and lowering. That enables
us to not lose edit-and-continue for existing switches.

The bound switch label now contains the value, as the labels cannot be relied on to contain the
constant values (e.g. synthesized labels do not, and we now synthesize switches for typeswitch).
Many places that work with bound switch statements had to be adjusted to consistently use the
constant in the bound switch label.

Fix parsing bug where `case A when B:` was parsed as a type pattern `A when` because `when` is
an identifier, followed by a syntax error (`B` seen but `:` expected). The fix is to never let a
pattern variable be named `where` at the top level of a switch.

Related to #12316

These tags were missing from the telemetry vsix and the setup.next vsix.

Now that the majority of our MicroBuild steps are in the open we can verify them at commit time.  This will guard us against more late night scrambles to fix the official build.