chore: Align StreamTrimAsync signatures with StackExchange.Redis in 2.0

[currantw]

Summary

Align StreamTrimAsync overload signatures exactly with StackExchange.Redis in the 2.0 release.

Description

Our current signatures differ from SER in two ways:

1. int overload has defaults (SER does not):

// Ours
Task<long> StreamTrimAsync(ValkeyKey key, int maxLength, bool useApproximateMaxLength = false, CommandFlags flags = CommandFlags.None);

// SER
Task<long> StreamTrimAsync(RedisKey key, int maxLength, bool useApproximateMaxLength, CommandFlags flags);

2. long overload uses long? with default (SER uses non-nullable long):

// Ours (from pre-1.2)
Task<long> StreamTrimAsync(ValkeyKey key, long? maxLength = null, ...);

// SER
Task<long> StreamTrimAsync(RedisKey key, long maxLength, ...);

These are source-breaking changes for callers who rely on the defaults, so they should be deferred to a major version.

Proposed Solution

In 2.0:

• Remove default values from the int overload parameters
• Change long? maxLength = null to long maxLength in the long overload

Related

• PR chore: Triage and clean up TODO comments #473 (identified during review)

[currantw]

Not needed — the long overload matches SER's actual signature (non-nullable, no default). No breaking change.