Rearrange sessionbuilder and tracing

[javiermtorres]

This is meant to be a basis for discussion about a preliminary rearrangement of ort session config and auxiliary services like tracing.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 43.24324% with 21 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
encoderfile/src/transport/cli.rs	0.00%	13 Missing ⚠️
encoderfile-runtime/src/main.rs	0.00%	3 Missing ⚠️
encoderfile/src/runtime/state.rs	82.35%	3 Missing ⚠️
encoderfile/src/runtime/loader.rs	0.00%	2 Missing ⚠️

Files with missing lines	Coverage Δ
encoderfile/src/builder/model.rs	91.83% <100.00%> (ø)
encoderfile/src/dev_utils/mod.rs	97.95% <100.00%> (ø)
encoderfile/src/runtime/loader.rs	64.00% <0.00%> (ø)
encoderfile-runtime/src/main.rs	0.00% <0.00%> (ø)
encoderfile/src/runtime/state.rs	77.27% <82.35%> (+3.19%)	⬆️
encoderfile/src/transport/cli.rs	0.00% <0.00%> (ø)

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[javiermtorres]

Ok, tracing will be kept as is. As for the rest:

we should make execution providers available on a per-binary basis.

Ok, so we'd enable flags in build saying something like "--ep=coreml" (or whatever). Then we can choose the specific provider and include it in the ef. This limits a bit the handiness of having a generic binary that can be customized for some specific model merely by changing the footer, but once the user gets one with the support they want, they can reuse it as much as they want.

Each binary that supports an EP should either use that EP or CPU at runtime (specified with a CLI command)

Ok, something like "--cpu"?

Are those n_intra_threads + parallel execution arguments new? They might be cpu-only

They could be. I've added them only as an example of onnx knobs we might be interested in when creating the session. I'm not sure we should expose all, some or any at all 😕

We should name GlobalState something else. Now we have 3 states and they will be easy to confuse 😬

Totally 😂 I didn't know what to name it, nor if you'd like to have some global state as such (we're not currently handling threads but we will). OnnxFactory could be a suggestion, but 1) let's check if we want indeed some global top state, and 2) let's choose a fancy name 😄

If you'd agree, I'll go for the top two first. We could limit the scope of this PR just to them, maybe, and replace the GlobalState with just a function returning the hardcoded SessionBuilder for the moment.