Add warn_on_resize option to DiffCache

[ChrisRackauckas-Claude]

Summary

• Adds a warn_on_resize::Bool field to DiffCache and a corresponding keyword argument (default true) to all constructors
• When warn_on_resize = false, the warning in enlargediffcache! is suppressed
• zero and copy preserve the warn_on_resize setting

Motivation

Adaptive BVP solvers (and other adaptive algorithms) expect cache expansion as normal behavior. Currently, downstream packages have to wrap get_tmp calls in Logging.with_logger(Logging.NullLogger()) to suppress the warning, which adds overhead and obscures the code:

# Current workaround in downstream packages
@inline function get_tmp(dc, u)
    return Logging.with_logger(Logging.NullLogger()) do
        PreallocationTools.get_tmp(dc, u)
    end
end

With this PR, they can simply construct the cache with warnings disabled:

dc = DiffCache(u; warn_on_resize = false)

Usage

# Default behavior (warns on resize) — backward compatible
dc = DiffCache(zeros(10))

# Suppress resize warnings for adaptive solvers
dc = DiffCache(zeros(10); warn_on_resize = false)

Test plan

• New tests verify warn_on_resize field is set correctly on construction
• warn_on_resize = false suppresses warning during cache enlargement (@test_nowarn)
• zero and copy preserve the warn_on_resize setting
• All existing tests pass

🤖 Generated with Claude Code