feat(inserter): add callback function support

[prnvbn]

Summary

Adds with_on_commit to the clickhouse inserter to hook a function call after a batch is actually committed (for e.g. bumping an OTEL metric tracking number of rows written to the database)

Addresses #306

[CLAassistant]

All committers have signed the CLA.

[abonander]

A couple of nits, otherwise looks fine.

[prnvbn]

@abonander addressed the comments

(P.S. I merged instead of a rebasing because I can see from the commit history that this PR will be squashed and merged)

[slvrtrn]

There are some failures with rustfmt and clippy; otherwise, it looks good

[prnvbn]

There are some failures with rustfmt and clippy; otherwise, it looks good

addressed most of them. suppressed one as per - #307 (comment)

[prnvbn]

@abonander, please review when you get the chance

[prnvbn]

bump on this

[abonander]

This looks good to me, but it's an open question whether we want to block this on adding a test.

I'm personally on the fence about it since the added functionality is rather trivial, so as long as inserts continue to function correctly (which is covered already) it doesn't seem like it needs a specific test.

But I'd like @slvrtrn's opinion on it before merging.

[slvrtrn]

Let's add more tests as a follow-up.