Implement InsertTabletsWithCtx for tablet insertion

[hchw]

Add InsertTabletsWithCtx method to insert multiple tablets with context support.

[HTHou]

Any motivation to add this function?

[hchw]

Any motivation to add this function?

To add a timeout to data writes, preventing function handles from being released because of write timeouts.

[hchw]

Why don't the functions you provide come with timeout control parameters?

[HTHou]

Thanks for the PR. I think the motivation is valid: the current InsertTablets path always uses context.Background(), while the generated thrift client already accepts a context.Context, so callers currently have no way to set a deadline or cancel a long-running write RPC.

That said, this looks like a partial API fix rather than a complete one. Other write methods such as InsertTablet, InsertAlignedTablet, InsertAlignedTablets, and InsertRecords still use context.Background() internally, so users would only get timeout/cancellation support for one insertion path. It may be better to add WithContext variants consistently for the main write APIs, with the existing methods delegating to them using context.Background().

One more detail worth documenting: this timeout would be a client-side RPC context timeout/cancellation. It lets the caller stop waiting and release client-side resources, but it does not necessarily guarantee that a request already received by the server is aborted server-side.