Add `--integrity.budget <duration>` to `erigon seg integrity` that caps
total wall-clock time for an integrity run.

- When set, checks are sorted cheap → heavy (based on
`integrity.FastChecks` order) and each receives a per-check deadline of
`remaining / remaining_checks`, so finishing early on a cheap check
rolls budget forward to the heavy tail.
- On per-check timeout: log `[integrity] budget exhausted, moving on` at
INFO and continue to the next check. Not treated as an integrity failure
— `--failFast` only reacts to actual integrity errors.
- When not set (default): no change in behavior — user-supplied order
preserved, no deadline applied.
- `BlockReader.IntegrityTxnID` now takes `ctx` and polls every 1000
segments so `BlocksTxnID` honors the budget.
- `CheckKvi` producer now checks `ctx` every 100k keys, so skip-heavy
runs (e.g. `CommitmentKvi` with `SampleRatio=0`) don't overshoot their
slice by minutes.
- `doPublishable` takes `datadir.Dirs` directly instead of
`*cli.Context`.

follow up:
- pick to release/3.4
- change automation script to allot 30min budget

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Co-authored-by: Alex Sharov <AskAlexSharov@gmail.com>