Improve cache context

[wolfogre]

Related to: #22294 #23186 #23054

Replace: #23218

Some discussion is in the comments of #23218.

Highlights:

• Add Expiration for cache context. If a cache context has been used for more than 10s, the cache data will be ignored, and warning logs will be printed.
• Add discard field to cacheContext, a cacheContext with discard true will drop all cached data and won't store any new one.
• Introduce WithNoCacheContext, if one wants to run long-life tasks, but the parent context is a cache context, WithNoCacheContext(perentCtx) will discard the cache data, so it will be safe to keep the context for a long time.
• It will be fine to treat an original context as a cache context, like GetContextData(context.Backgraud()), no warning logs will be printed.

Some cases about nesting:

When:

• A, B or C means a cache context.
• A, B or C means a discard cache context.
• ctx means context.Backgrand()
• A(ctx) means a cache context with ctx as the parent context.
• B(A(ctx)) means a cache context with A(ctx) as the parent context.
• With means WithCacheContext
• WithNo means WithNoCacheContext

So:

• With(ctx) -> A(ctx)
• With(With(ctx)) -> A(ctx), not B(A(ctx))
• With(With(With(ctx))) -> A(ctx), not C(B(A(ctx)))
• WithNo(ctx) -> ctx, not A(ctx)
• WithNo(With(ctx)) -> A(ctx)
• WithNo(WithNo(With(ctx))) -> A(ctx), not B(A(ctx))
• With(WithNo(With(ctx))) -> B(A(ctx))
• WithNo(With(WithNo(With(ctx)))) -> B(A(ctx))
• With(WithNo(With(WithNo(With(ctx))))) -> C(B(A(ctx)))

[wxiaoguang]

The description seems very valuable. Maybe the description could be put into code as package comment? If would help future developers when they are using the package.

[jolheiser]

🎺 🤖