2046_fabricx_public_params_setup_returns_errors

[HayimShaul]

Fixes #2046

fabricx.Backend.InstallPublicParams and UpdatePublicParams panicked instead of
reporting failures: UpdatePublicParams dereferenced a nil issuer client, both panicked on
a SetupPublicParams view error, and the install variant did so from a background
goroutine, which took the whole test process down with panic: failed updating pps.

Both now return an error, and so does the fabric.Backend interface they implement:

• the background installation is crash-safe (recover()) and records its outcome per TMS;
  WaitForPublicParams blocks on it, PendingInstallError polls it;
• UpdatePublicParams waits for the issuer client the way the install path does, so a
  not-yet-started issuer node is a wait rather than a nil-interface panic. The retry budget
  is configurable (ClientRetries, ClientRetryDelay, InstallDelay), defaulting to
  today's 60 attempts / 1s / 10s;
• fabric.NetworkHandler converts the errors into gomega failures (PostRun,
  UpdatePublicParams) and logs a still-pending install failure in Cleanup, so the NWO
  platform API is unchanged;
• cc.GenericBackend follows the new signatures and returns its chaincode lookup,
  mkdir and packaging failures as errors;
• the view payload is marshalled with encoding/json instead of common.JSONMarshall,
  whose failure mode is a gomega assertion — another hidden panic on this very path.

Behaviour change worth calling out: an installation that failed in the background used to
crash the run, or pass unnoticed. It now fails the spec that updates the public parameters,
carrying the original error, or is logged at teardown.

Tests: integration/nwo/token/fabricx/factory_test.go covers both paths, a recovered
panic, the wait timeout and the exact payload sent to the view.
TestInstallPublicParamsBackgroundFailureDoesNotCrashProcess re-executes the failing
installation in a child process — the only way to assert that the goroutine no longer kills
the runner — and it fails if the panic is reintroduced.

make checks is green. make lint reports only findings already present on main
(verified by linting a clean origin/main worktree); this change adds none.

Docs: docs/development/debug-integration-tests.md gains a section on where a public
parameters setup failure now surfaces.