Add generic Random NextInteger/NextBinaryFloat APIs

[stephentoub]

Adds generic numeric APIs to System.Random:

• NextInteger<T>()
• NextInteger<T>(T maxValue)
• NextInteger<T>(T minValue, T maxValue)
• NextBinaryFloat<T>().

Fixes #75431

[Copilot]

Pull request overview

This PR adds new generic numeric APIs to System.Random to generate random integer values for any IBinaryInteger<T> and random IEEE-754 binary floating-point values for any IBinaryFloatingPointIeee754<T>.

Changes:

• Add Random.NextInteger<T>(), Random.NextInteger<T>(T maxValue), and Random.NextInteger<T>(T minValue, T maxValue) with fast paths for common integer types and generic rejection-sampling fallbacks.
• Add Random.NextBinaryFloat<T>() with fast paths for float/double/NFloat and a generic implementation that guarantees results in [0, 1).
• Update reference assembly API surface and add unit tests covering edge cases, large ranges, and derived Random dispatch behavior.

Show a summary per file

File	Description
src/libraries/System.Private.CoreLib/src/System/Random.cs	Implements the new generic integer and binary-float generation APIs, including fast paths and fallbacks.
src/libraries/System.Runtime/ref/System.Runtime.cs	Exposes the new Random APIs in the System.Runtime reference assembly.
src/libraries/System.Runtime/tests/System.Runtime.Extensions.Tests/System/Random.cs	Adds coverage for argument validation, boundary/range behavior, and derived Random virtual dispatch; also introduces helper numeric wrapper types for custom reference-type coverage.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 3