[wasm-split] Fix table naming conflicts

[aheejin]

After #8688, we split module elements, including tables, earlier than indirectCallsToSecondaryFunctions, which calls getSlot, which calls makeTable. But when making a table, we only try to get a valid name within the primary module:

binaryen/src/ir/module-splitting.cpp

Lines 235 to 238 in 2f1f55a

	Table* TableSlotManager::makeTable() {
	return module.addTable(
	Builder::makeTable(Names::getValidTableName(module, Name::fromInt(0))));
	}

If an existing table's name was 0 and it was moved to a secondary module in shareImportable already, this will happily create an active table with the name 0 again. And in setupTablePatching, because the secondary module already has 0, the active table will not be exported / imported there:

binaryen/src/ir/module-splitting.cpp

Lines 1103 to 1117 in 2f1f55a

	// Import and export the active table if necessary. Unless we use an
	// existing table as an active table (e.g. because reference-types is
	// disabled) and that table was already being used by an existing indirect
	// call, shareImportableItems wasn't able to mark it as used in secondaries,
	// so we should export and import the active table here.
	auto secondaryTable =
	secondary.getTableOrNull(tableManager.activeTable->name);
	if (!secondaryTable) {
	secondaryTable =
	ModuleUtils::copyTable(tableManager.activeTable, secondary);
	makeImportExport(*tableManager.activeTable,
	*secondaryTable,
	"table",
	ExternalKind::Table);
	}

But this existing table is NOT the active table, and this table's type may not even be funcref.

This fixes makeTable so that it makes a table name that does not collide with any table names not only in the primary module but all secondary modules.

This also disables Split fuzzer for now; I'm finding more bugs, so I'll reenable it after it is more stabilized.

[aheejin]

Table names are not actually shown in the output because its hasExternalName is false. But without this patch this test crashes because it tries to reuse the existing externref table in the secondary module as the active table.

[tlively]

Are you saying that $0 is not the internal name of the table? Why are we emitting a name at all, then?

[tlively]

We don't want to iterate through all the secondaries multiple times in case it takes several iterations to find a good name. Let's iterate through them just once and create a set of all the table names we have to avoid.

[aheejin]

But we only create an active table once, no?

[tlively]

Right. I mean that we should create this set just once at the beginning of makeTable. getValidName() can call the predicate an arbitrary number of times until it finds a valid name, so we want to avoid that being pathologically expensive.

[tlively]

It looks like the new table is still called $0?

[aheejin]

#8708 (comment)
We can set hasExternalName true depending on the debug information. Given that there will be only one active table, I'm not sure if it's worth it, but we can try, like even naming it "active_table" and make it shown in debug mode. (But this would be better as a follow-up, if we do it)