llama.cpp: add model_converters variant

[i0ntempest]

Description

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS x.y
Xcode x.y / Command Line Tools x.y.z

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@blair for port py-tensorflow_estimator.
@mdouze for port libfaiss.
@beauby for port libfaiss.
@emcrisostomo for port py-absl, py-tensorboard.
@cjones051073 for port py-blis, py-confection, py-plac, py-preshed, py-srsly, py-thinc, py-wasabi.
@reneeotten for port py-cookiecutter.
@stromnov for port py-scikit-learn.

[i0ntempest]

@mascguy Please take a look!
This massive PR took me like 2 days, and there's almost certainly something that I fricked up. For one I cannot track the dependency relations of all the python ports I changed anymore.
What I've done:
Ran through all the dependencies needed for the four conversion scripts to work, adding compatibility up to Python 3.12 (or 3.13 if the package supports it), and updating them if possible.

What I've tested and works:

1. Importing gguf, torch, tensorflow, transformers in python
2. Running the tensorflow test script from Apple here
3. Running all the conversion scripts without args (that is I did not test any actual conversions)

Some notes:

1. py-preshed must be downgraded for py-spaCy to build
2. py-tensorflow-macos was updated to use tensorflow pypi instead of tensorflow-macos, which seems defunct. This is the only way we can get to python 3.12, and I didn't dare touch the actual py-tensorflow port
3. Multiple build workarounds needed because our numpy is ancient
4. Old protobuf3-cpp blocked me from updating grpc

[mascguy]

I'll take a closer look.

Also adding @essandess for review/comment, as he's contributed to a number of Python ports in this space.

[i0ntempest]

I haven’t ironed out all the problems yet but all 3 CI tests fail at 381 minutes, is this a timeout?
Also I can’t see any log from 15.0 CI.

[i0ntempest]

Well this is taking too long. How about we just ship the scripts and leave the environment setup to users? I mean most are using venv for this kind of stuff anyways.

[mascguy]

Well this is taking too long. How about we just ship the scripts and leave the environment setup to users? I mean most are using venv for this kind of stuff anyways.

Works for me!