[refurb] Parse more exotic decimal strings in verbose-decimal-constructor (FURB157) (#14098)

FURB157 suggests replacing expressions like `Decimal("123")` with
`Decimal(123)`. This PR extends the rule to cover cases where the input
string to `Decimal` can be easily transformed into an integer literal.

For example:

```python
Decimal("1__000")   # fix: `Decimal(1000)`
```

Note: we do not implement the full decimal parsing logic from CPython on
the grounds that certain acceptable string inputs to the `Decimal`
constructor may be presumed purposeful on the part of the developer. For
example, as in the linked issue, `Decimal("١٢٣")` is valid and equal to
`Decimal(123)`, but we do not suggest a replacement in this case.

Closes #13807

crates/ruff_linter/resources/test/fixtures/refurb/FURB157.py

@@ -15,3 +15,23 @@ decimal.Decimal("0")
 Decimal(0)
 Decimal("Infinity")
 decimal.Decimal(0)
+
+# Handle Python's Decimal parsing
+# See https://github.com/astral-sh/ruff/issues/13807
+
+# Errors
+Decimal("1_000")
+Decimal("__1____000") 
+
+# Ok
+Decimal("2e-4")
+Decimal("2E-4")
+Decimal("_1.234__")
+Decimal("2e4")
+Decimal("2e+4")
+Decimal("2E4")
+Decimal("1.2") 
+# Ok: even though this is equal to `Decimal(123)`,
+# we assume that a developer would
+# only write it this way if they meant to.
+Decimal("١٢٣")