Update testsuite

[keithw]

Sequenced behind #2272.

This updates the testsuite. The major changes:

• The exception-handling tests now require tail-calls (tbd in wasm2c: implement the tail-call proposal #2272).
• There's a new test (memory_copy1 from multi-memory), which required Flip order of memory indexes on memory.copy per upstream #2294 (now merged).
• The elem tests now use global.get in an elem expr, which required Share reading/validation code between elem exprs & other const exprs #2288 (now merged).

(The only missing test is relaxed-simd/relaxed_dot_product.txt, which it looks like we believe is going away per #2115.)

[keithw]

Reverting to draft as I think there may be a cleaner way to do the global.get change, and in any event I'll try to split this one up.

[sbc100]

Rubberstamp lgtm