Repro for shared WebSocket session failure in workerd

[edmundhung]

Related to #158

This adds 3 tests to reproduce the behavior under large payload volume:

# failing workerd case using one shared WebSocket session under large payload volume
pnpm test -- --project workerd __tests__/workerd.test.ts -t "fails with a shared websocket session"

# passing workerd control using fresh WebSocket sessions per batch
pnpm test -- --project workerd __tests__/workerd.test.ts -t "passes with a fresh websocket session per batch"

# passing Node control using the same shared WebSocket session pattern
pnpm test -- --project node __tests__/index.test.ts -t "same high-byte-volume workload in Node"

For the failing test, you should see something like this:

[vpw:info] Starting isolated runtimes for 1...

<--- Last few GCs --->

[16746:0xbf21f4000]     1353 ms: Mark-Compact 1399.4 (1423.0) -> 1399.4 (1423.0) MB, pooled: 2.2 MB, 2.02 / 0.00 ms (average mu = 0.113, current mu = 0.000) allocation failure; GC in old space requested
[16746:0xbf21f4000]     1355 ms: Mark-Compact 1399.4 (1423.0) -> 1399.4 (1423.0) MB, pooled: 2.2 MB, 2.02 / 0.00 ms (average mu = 0.060, current mu = 0.001) allocation failure; GC in old space requested

workerd/jsg/setup.c++:38: fatal: V8 fatal error; location = Ineffective mark-compacts near heap limit; message = : allocation failed: JavaScript heap out of memory
*** Received signal #6: Abort trap: 6
stack: 19b073887 19af7884f 1038d1f0f 103d0c18b 103ee937f 103ee765b 103efb6a3 103efb42b 103efaf47 103ed0cb7 103fe8cfb 103fef2ff 103fef3eb 103fef3eb 103fe86db 103fe8417 103d85a23 103bd960b 170286f8f 103b75983 103c50977 103b6601b 103b3addb 103e550cf 103e559ab 103e55aeb 103e6b10f 103e6af7b 1038aa7cf

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Unhandled Rejection ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
TypeError: fetch failed
 ❯ node_modules/.pnpm/undici@7.18.2/node_modules/undici/index.js:127:13
 ❯ process.processTicksAndRejections node:internal/process/task_queues:105:5
 ❯ MessagePort.<anonymous> [worker eval]:28:22

Caused by: Error: connect ECONNREFUSED 127.0.0.1:55534
 ❯ TCPConnectWrap.afterConnect [as oncomplete] node:net:1637:16

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