nonblocking dynamic imports

[karlseguin]

Allows dynamic imports to be loading asynchronously. I know reddit isnt the best example, since it doesn't fully load, but this reduced the load time from ~7.2s to ~4.8s.

[krichprollsch]

I'm testing it with zig build run -- fetch --log_level debug https://www.reddit.com/r/Zig/comments/1npm8e3/dyld47130_segment_const_zig_vm_address_out_of and I get a v8 crash I don't have in main

#
# Fatal error in ../../../src/src/objects/objects.cc, line 4509
# Debug check failed: Holder<To> v8::internal::Cast(Holder<From>, const v8::SourceLocation &) [To = v8::internal::Union<v8::internal::Smi, v8::internal::HeapNumber, v8::internal::BigInt, v8::internal::String, v8::internal::Symbol, v8::internal::Boolean, v8::internal::Null, v8::internal::Undefined, v8::internal::JSReceiver>, From = v8::internal::Object, Holder = v8::internal::Tagged].
#
#
#
#FailureMessage Object: 0x7ffcec98a300
==== C stack trace ===============================

    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3af3463]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3af143d]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3b64f74]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3b64915]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3f173e1]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3c5068e]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3ae3ded]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x3390083]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x32b159a]
    ./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda() [0x6c930c7]
run
└─ run exe lightpanda failure
error: the following command terminated unexpectedly:
./.zig-cache/o/ae50c4e101ff79b6525507fb93b79753/lightpanda fetch --log_level debug https://www.reddit.com/r/Zig/comments/1npm8e3/dyld47130_segment_const_zig_vm_address_out_of/

Build Summary: 3/5 steps succeeded; 1 failed
run transitive failure
└─ run exe lightpanda failure

[karlseguin]

I'm testing it with zig build run -- fetch --log_level debug https://www.reddit.com/r/Zig/comments/1npm8e3/dyld47130_segment_const_zig_vm_address_out_of and I get a v8 crash I don't have in main

i was able to reproduce this unreliably. Even the HTML.HtmlScriptElement test would fail ~ 1/50 times. After the latest change, I haven't see the crash in either the test or on reddit, but I'm not 100% confident.