feat(tests): auto-merge all model list responses and unify recordings (#3320)

One needed to specify record-replay related environment variables for
running integration tests. We could not use defaults because integration
tests could be run against Ollama instances which could be running
different models. For example, text vs vision tests needed separate
instances of Ollama because a single instance typically cannot serve
both of these models if you assume the standard CI worker configuration
on Github. As a result, `client.list()` as returned by the Ollama client
would be different between these runs and we'd end up overwriting
responses.

This PR "solves" it by adding a small amount of complexity -- we store
model list responses specially, keyed by the hashes of the models they
return. At replay time, we merge all of them and pretend that we have
the union of all models available.

## Test Plan

Re-recorded all the tests using `scripts/integration-tests.sh
--inference-mode record`, including the vision tests.

tests/integration/recordings/responses/9e7a83d3d596.json

@@ -15,23 +15,23 @@
     "body": {
       "__type__": "openai.types.completion.Completion",
       "__data__": {
-        "id": "cmpl-43",
+        "id": "cmpl-775",
         "choices": [
           {
             "finish_reason": "stop",
             "index": 0,
             "logprobs": null,
-            "text": "Blue.\n\nMy response is based on the traditional English rhyme that pairs the colors of roses (red) with violets in a poetic and somewhat whimsical way. This specific version of the rhyme goes like this:\n\n\"Roses are red,\nViolets are blue,\nSugar is sweet,\nAnd so are you.\"\n\nIn modern times, variations of this rhyme can deviate from the original \"blue\" for violets, but in my complete sentence as requested, sticking with a widely recognized completion adds an air of timelessness and familiarity to the phrase."
+            "text": "Blue.\n\nMy response is based on the traditional rhyme \"Roses are Red, Violets are Blue,\" which is a well-known poem or phrase often used as a greeting or way to express affection. The exact wording may vary slightly depending on the source, but the general meaning remains the same: violets are typically depicted as blue-colored flowers in this rhyme."
           }
         ],
-        "created": 1754348148,
+        "created": 1756921025,
         "model": "llama3.2:3b-instruct-fp16",
         "object": "text_completion",
         "system_fingerprint": "fp_ollama",
         "usage": {
-          "completion_tokens": 113,
+          "completion_tokens": 75,
           "prompt_tokens": 50,
-          "total_tokens": 163,
+          "total_tokens": 125,
           "completion_tokens_details": null,
           "prompt_tokens_details": null
         }