Add Tiktoken Synchronous Creation Using Model Name

[tarekgh]

Fixes https://github.com/dotnet/machinelearning/issues/7077

The change:

• Adding a new method Tiktoken.CreateTokenizerByModelName allow synchronous creation of the tokenizer using the model name.
• Renaming Tiktoken.CreateByModelNameAsync to Tiktoken.CreateTokenizerByModelNameAsync. This adjustment is being made because the Tiktoken class includes other methods for creating models, not just tokenizers. By adding the word Tokenizer to the method responsible for creating a tokenizer, it will provide clarity regarding its functionality.

[tarekgh]

CC @tonybaloney @ericstj @michaelgsharp

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 82.25806% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 68.82%. Comparing base (8b483f4) to head (3038075).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7080 +/- ## ======================================= Coverage 68.82% 68.82% ======================================= Files 1255 1255 Lines 250358 250400 +42 Branches 25550 25554 +4 ======================================= + Hits 172310 172344 +34 - Misses 71438 71443 +5 - Partials 6610 6613 +3 ``` | [Flag](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | Coverage Δ | | |---|---|---| | [Debug](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `68.82% <82.25%> (+<0.01%)` | :arrow_up: | | [production](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `63.26% <68.57%> (+<0.01%)` | :arrow_up: | | [test](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `88.51% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | Coverage Δ | | |---|---|---| | [...crosoft.ML.Tokenizers/Utils/Helpers.netstandard.cs](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#diff-c3JjL01pY3Jvc29mdC5NTC5Ub2tlbml6ZXJzL1V0aWxzL0hlbHBlcnMubmV0c3RhbmRhcmQuY3M=) | `81.81% <100.00%> (+0.56%)` | :arrow_up: | | [test/Microsoft.ML.Tokenizers.Tests/TitokenTests.cs](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#diff-dGVzdC9NaWNyb3NvZnQuTUwuVG9rZW5pemVycy5UZXN0cy9UaXRva2VuVGVzdHMuY3M=) | `100.00% <100.00%> (ø)` | | | [src/Microsoft.ML.Tokenizers/Model/Tiktoken.cs](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#diff-c3JjL01pY3Jvc29mdC5NTC5Ub2tlbml6ZXJzL01vZGVsL1Rpa3Rva2VuLmNz) | `68.55% <67.64%> (+0.83%)` | :arrow_up: | ... and [5 files with indirect coverage changes](https://app.codecov.io/gh/dotnet/machinelearning/pull/7080/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet)

[tarekgh]

I filed https://github.com/dotnet/machinelearning/issues/7084 for the failures but build analysis didn't enable to squash and merge.