Handle return calls correctly

This is a combined commit covering multiple PRs fixing the handling of return
calls in different areas. The PRs are all landed as a single commit to ensure
internal consistency and avoid problems with bisection.

Original PR descriptions follow:

* Fix inlining of `return_call*` (#6448)

Previously we transformed return calls in inlined function bodies into normal
calls followed by branches out to the caller code. Similarly, when inlining a
`return_call` callsite, we simply added a `return` after the body inlined at the
callsite. These transformations would have been correct if the semantics of
return calls were to call and then return, but they are not correct for the
actual semantics of returning and then calling.

The previous implementation is observably incorrect for return calls inside try
blocks, where the previous implementation would run the inlined body within the
try block, but the proper semantics would be to run the inlined body outside the
try block.

Fix the problem by transforming inlined return calls to branches followed by
calls rather than as calls followed by branches. For the case of inlined return
call callsites, insert branches out of the original body of the caller and
inline the body of the callee as a sibling of the original caller body. For the
other case of return calls appearing in inlined bodies, translate the return
calls to branches out to calls inserted as siblings of the original inlined
body.

In both cases, it would have been convenient to use multivalue block return to
send call parameters along the branches to the calls, but unfortunately in our
IR that would have required tuple-typed scratch locals to unpack the tuple of
operands at the call sites. It is simpler to just use locals to propagate the
operands in the first place.

* Fix interpretation of `return_call*` (#6451)

We previously interpreted return calls as calls followed by returns, but that is
not correct both because it grows the size of the execution stack and because it
runs the called functions in the wrong context, which can be observable in the
case of exception handling.

Update the interpreter to handle return calls correctly by adding a new
`RETURN_CALL_FLOW` that behaves like a return, but carries the arguments and
reference to the return-callee rather than normal return values.
`callFunctionInternal` is updated to intercept this flow and call return-called
functions in a loop until a function returns with some other kind of flow.

Pull in the upstream spec tests return_call.wast, return_call_indirect.wast, and
return_call_ref.wast with light editing so that we parse and validate them
successfully.

* Handle return calls in wasm-ctor-eval (#6464)

When an evaluated export ends in a return call, continue evaluating the
return-called function. This requires propagating the parameters, handling the
case that the return-called function might be an import, and fixing up local
indices in case the final function has different parameters than the original
function.

* Update effects.h to handle return calls correctly (#6470)

As far as their surrounding code is concerned return calls are no different from
normal returns. It's only from a caller's perspective that a function containing
a return call also has the effects of the return-callee. To model this more
precisely in EffectAnalyzer, stash the throw effect of return-callees on the
side and only merge it in at the end when analyzing the effects of a full
function body.

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