sync: add --concurrency and --retry-timeout flags

[luketchang]

The sync engine hardcoded its in-flight request limit at 20 and relied on the SDK's retry layer, which only retries 429 and 504 (databricks-sdk-go httpclient/errors.go DefaultErrorRetriable). 502 and 503 surface as fatal errors that fail the entire sync.

• Add SyncOptions.Concurrency and SyncOptions.RetryTimeout; default to MaxRequestsInFlight and DefaultRetryTimeout respectively when zero so existing in-process callers (bundle deploy/files) need no changes.
• Wrap each filer call (PUT, delete, mkdir, rmdir) in retries.Poll, retrying on 502/503/504 within the deadline and logging each retry at warn level. Uses the same retries.Poll helper used elsewhere in the CLI for state polling.
• Surface --concurrency (default 5) and --retry-timeout (default 30s) on 'databricks sync' and 'databricks bundle sync'.

429 stays out of the new retry layer because the SDK already handles it with rate-limit-aware backoff. 500 stays out because it is not always transient for Databricks APIs.

Slack thread:
https://replit.slack.com/archives/C0A2Z9042FR/p1778082184841149

Changes

Why

Tests

[github-actions]

An authorized user can trigger integration tests manually by following the instructions below:

Trigger:
go/deco-tests-run/cli

Inputs:

• PR number: 5201
• Commit SHA: 7566146e6647a5f480ea298e0d45ad4407d75c3b

Checks will be approved automatically on success.

[github-actions]

Approval status: pending

/cmd/bundle/ - needs approval

Files: cmd/bundle/sync.go
Suggested: @pietern
Also eligible: @denik, @anton-107, @shreyas-goenka, @andrewnester, @janniklasrose, @lennartkats-db

/cmd/sync/ - needs approval

Files: cmd/sync/sync.go
Suggested: @simonfaltum
Also eligible: @renaudhartert-db, @hectorcast-db, @parthban-db, @tanmay-db, @Divyansh-db, @tejaskochar-db, @mihaimitrea-db, @chrisst, @rauchy

/libs/sync/ - needs approval

4 files changed
Suggested: @simonfaltum
Also eligible: @renaudhartert-db, @hectorcast-db, @parthban-db, @tanmay-db, @Divyansh-db, @tejaskochar-db, @mihaimitrea-db, @chrisst, @rauchy

_{Any maintainer (@andrewnester, @anton-107, @denik, @pietern, @shreyas-goenka, @simonfaltum, @renaudhartert-db) can approve all areas.
See OWNERS for ownership rules.}