FHE Regex Pattern Matching Engine

[RKlompUU]

Most important locations:

• the tutorial is in tfhe/docs/regex/tutorial.md
• the example implementation is in tfhe/src/regex/..

Not quite sure if you want the example implementation to be under tfhe/src directly (how it is in this PR atm), or to have it be more of an external dependency (like how I initially had set it up in a separate repo). Let me know.

I might still want to add a Further work section at the end of the tutorial, and to add some comments to the code. But I think it's best to open this PR now to get the final review process started.

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To run the included tests run: cargo test --release --features=x86_64,integer --example regex_engine.

[IceTDrinker]

first request for this PR: squash in a single commit and follow the commit message format, in that case it should be

docs(tfhe): add FHE Regex Pattern Matching Engine

(... more details)

[tmontaigu]

I still need to review a bit more deeply I looked good from what i've seen so far, I've made some comments.

Not quite sure if you want the example implementation to be under tfhe/src directly (how it is in this PR atm), or to have it be more of an external dependency (like how I initially had set it up in a separate repo). Let me know.

Yes we would prefer the implementation to be more separated from the lib.
Normally you should be able to have all your code under a sub folder of the examples folder
You could take at look at this other bounty where its organized in the example folder #283

[RKlompUU]

I addressed each comment that's been left here so far.

I moved the example implementation from src/regex to examples/regex_engine. This did mean that the final section of the tutorial made no sense anymore as far as I can tell. Instead I replaced that with a section on how to run the example implementation.

[aquint-zama]

closes zama-ai/bounty-program#38