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Add preflight EXPLAIN check to table editor rows (#42321)

## Context

Part of an investigation to see how we can make the dashboard more
resilient for large databases by ensuring that the dashboard never
becomes the reason for taking down the database accidentally.

Am proposing that for interfaces that rely heavily on queries to the
database for data to render, we add preflight checks to ensure that we
never run queries that exceed a certain cost threshold (and also have UI
handlers to communicate this) - this can be done by running an EXPLAIN
query before running the actual query, and if the cost from the EXPLAIN
exceeds a specified threshold, the UI throws an error then and skips
calling the actual query.

## Demo
Am piloting this with the Table Editor, and got an example here in which
my table has 500K+ rows, and I'm trying to sort on an unindexed column:


https://github.com/user-attachments/assets/ccad2ea9-d62c-4106-8295-2a6df5941474

With this UX, the pros are that
- It's relatively seamless and not too invasive, most users won't notice
this unless they run into this specific scenario
- We can incrementally apply this to other parts of the dashboard, next
will probably be Auth Users for example

However there are some considerations:
- The additional EXPLAIN query adds a bit more latency to the query
since its a separate API request to the query endpoint
- ^ On a similar note, it will hammer the API a bit more, which may
result in higher probability of 429s
- However, I reckon that the preflight checks are meant to be used
sparingly and only for certain parts of the dashboard that we believe
may cause high load.
- e.g for the Table Editor, reckon we only need this for fetching rows?
The count query is largely optimized already (although we could just add
a preflight check there too)
- It's just meant to be a safeguard to prevent running heavy queries on
the database



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