Drop the re-exports so there is one import path per symbol

[cboulay]

Follow-up to #240, taking you up on the offer to break 3.8.0/3.8.1's added surface rather than live with two import paths.

What was wrong with the re-exports

3.8.1 re-exported baseproc's resolvers and suppress_axis_deprecation from ezmsg.sigproc.util.* for compatibility with 3.8.0, which had defined them there. That compatibility bought less than the confusion it cost.

The concrete failure: while 3.8.0 was current there were two different ContextVars behind the same name. ezmsg-event entered baseproc's suppression context, sigproc's warning checked sigproc's — so nothing was suppressed and the forwarding warned twice. CI caught it; my local editable install had masked it. The fix at the time was a four-line comment in event and learn explaining which of two mechanisms to reach for. That comment is what this PR deletes.

Both releases are a day old and none of these symbols existed before them.

The end state

symbol	single source
resolve_chunk_dim, resolve_feature_dim, resolve_transform_dim, resolve_configured_chunk_dim, STREAMING_DIMS	ezmsg.baseproc
suppress_axis_deprecation	ezmsg.baseproc
AXIS_REMOVAL_VERSION, warn_axis_deprecated	ezmsg.sigproc.util.deprecation

The remaining warn_axis_deprecated is not a re-export — it binds baseproc's to this distribution and its removal release, so ~27 call sites stay one line and every message agrees on when the setting goes away. Its docstring now says so explicitly.

The sample-message re-exports in util.message (SampleMessage, SampleTriggerMessage, is_sample_message) are untouched: those predate all of this and have real users.

Notes

Net −12 lines across 34 files; ruff collapsed the split imports back into single from ezmsg.baseproc import (...) blocks, so most files got shorter.

One import my rewrite pattern missed: util/channels.py used from .message import resolve_feature_dim — relative within util/, so it didn't match from .util.message import. Collection failed loudly and it's fixed.

Testing

4285 unit + 51 integration pass; ruff clean. Verified the surface is actually gone rather than just unused — ezmsg.sigproc.util.message and .deprecation no longer expose any resolver or the suppression context.

Downstream, ezmsg-event and ezmsg-learn now import suppression from baseproc and pin >=3.8.1; both suites pass against the real 3.8.1 wheel.