gh-73487: Convert _decimal to use Argument Clinic (part 6)

[skirpichev]

• Issue: decimal: Use Argument Clinic #73487

[serhiy-storchaka]

LGTM. 👍

[skirpichev]

Docstrings diff:

--- ref.txt 2025-08-22 11:00:56.325746547 +0300+++ patch.txt 2025-08-22 10:49:32.335072600 +0300@@ -95,6 +95,8 @@ | traps=None | ) | + | Create context.+ | | The context affects almost all operations and controls rounding, | Over/Underflow, raising of exceptions and much more. A new context | can be constructed as follows: @@ -182,12 +184,16 @@ | Copy the sign from y to x. | | create_decimal(self, num='0', /) - | Create a new Decimal instance from num, using self as the context. Unlike the- | Decimal constructor, this function observes the context limits.+ | Create a new Decimal instance from num, using self as the context.+ |+ | Unlike the Decimal constructor, this function observes the context+ | limits. | | create_decimal_from_float(self, f, /) - | Create a new Decimal instance from float f. Unlike the Decimal.from_float()- | class method, this function observes the context limits.+ | Create a new Decimal instance from float f.+ |+ | Unlike the Decimal.from_float() class method, this function observes+ | the context limits. | | divide(self, x, y, /) | Return x divided by y.