The {CodeSpaceWriteScope} in {InstanceBuilder::Build} was kept open
while processing imports, which could compile another wasm module via
{compiler::ResolveWasmImportCall} and
{WasmEngine::SyncCompileTranslatedAsmJs}. This leads to errors since
{CodeSpaceWriteScope}s for different modules cannot be held open at the
same time.

This CL fixes that by only opening the {CodeSpaceWriteScope} for the
actual compilation of import wrappers.

Drive-by: Only call {ProcessImports} if there are imports to be
processed, to avoid some of the overhead of {ProcessImports} and
{CompileImportWrappers}.

R=jkummerow@chromium.org

Bug: chromium:1239522
Change-Id: Ifbaf64a4be92088ae4a3fd7e9700a33397b2a967
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3097283
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76311}