feat(python): detect and warn about usage of json.loads in conjunction with apply

[alexander-beedie]

Ref: #9968.

Detects/handles both formulations...

• pl.col("foo").apply(json.loads)
• pl.col("foo").apply(lambda x: json.loads(x))

...resulting in (json.loads)...

# PolarsInefficientApplyWarning: 
# Expr.apply is significantly slower than the native expressions API.
# Only use if you absolutely CANNOT implement your logic otherwise.
# In this case, you can replace your `apply` with an expression:
#   -  pl.col("foo").apply(json.loads)
#   +  pl.col("foo").str.json_extract()

...or (wrapped in lambda):

# In this case, you can replace your `apply` with an expression:
#   -  pl.col("foo").apply(lambda x: ...)
#   +  pl.col("foo").str.json_extract()

[alexander-beedie]

Ahh… Will fix-up the unit tests that now fail (as they use json.loads via apply) in the morning.

Update: done 👍

[MarcoGorelli]

it keeps getting better