feat: allow target MAX_SIZE_DEFAULT to be externally configurable

[pnadolny13]

In the base sink class we define a MAX_SIZE_DEFAULT thats set to 10,000

sdk/singer_sdk/sinks/core.py

Line 133 in e9f2c17

MAX_SIZE_DEFAULT = 10000

. Thats a fine base default and target developers can override it if their target prefers smaller or larger batches.

The thing thats not supported today is the use case where I want to configure a target, say target-postgres, to output more frequently because my tap records are slow/expensive to get so the possibility of waiting until 10k records are retrieved, the batch is old enough to drain, or the sync completes, is undesirable. I might want to drain after every 50 records or so in some case.

One example that came up a while ago is from the map-gpt-embeddings plugin that requests from openai's api. It takes a while to embed all input data and each request costs money so preferably I'd drain as frequently as possible.

cc @edgarrmondragon

[BuzzCutNorman]

@pnadolny13 if you are able to would you mind giving PR #1876 a try with a target and to see if it works to satisfies your scenario?