[GenAI] Add LLaMA support

[LittleLittleCloud]

We are excited to review your PR.

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• There's a descriptive title that will make sense to other developers some time from now.
• There's associated issues. All PR's should have issue(s) associated - unless a trivial self-evident change such as fixing a typo. You can use the format Fixes #nnnn in your description to cause GitHub to automatically close the issue(s) when your PR is merged.
• Your change description explains what the change does, why you chose your approach, and anything else that reviewers should know.
• You have included any necessary tests in the same PR.

#7169

[codecov]

Codecov Report

Attention: Patch coverage is 40.34166% with 454 lines in your changes missing coverage. Please review.

Project coverage is 68.83%. Comparing base (fa8c822) to head (19a2d7e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Microsoft.ML.GenAI.LLaMA/Module/LlamaModel.cs	18.75%	76 Missing and 2 partials ⚠️
...crosoft.ML.GenAI.LLaMA/Module/LlamaDecoderLayer.cs	28.57%	65 Missing ⚠️
src/Microsoft.ML.GenAI.LLaMA/LlamaCausalLMAgent.cs	0.00%	50 Missing ⚠️
src/Microsoft.ML.GenAI.LLaMA/LlamaForCausalLM.cs	14.03%	49 Missing ⚠️
...osoft.ML.GenAI.LLaMA/LlamaTextCompletionService.cs	0.00%	41 Missing ⚠️
.../Microsoft.ML.GenAI.Core/Module/RotaryEmbedding.cs	42.62%	34 Missing and 1 partial ⚠️
...crosoft.ML.GenAI.Core/Extension/ModuleExtension.cs	0.00%	29 Missing ⚠️
src/Microsoft.ML.GenAI.Core/Module/Attention.cs	40.00%	24 Missing ⚠️
...osoft.ML.GenAI.LLaMA/LlamaChatCompletionService.cs	0.00%	19 Missing ⚠️
...soft.ML.GenAI.LLaMA/Llama3_1ChatTemplateBuilder.cs	68.62%	8 Missing and 8 partials ⚠️
... and 11 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7220      +/-   ##
==========================================
- Coverage   68.89%   68.83%   -0.07%     
==========================================
  Files        1441     1453      +12     
  Lines      270827   271482     +655     
  Branches    28019    28090      +71     
==========================================
+ Hits       186584   186870     +286     
- Misses      77038    77393     +355     
- Partials     7205     7219      +14     

Flag	Coverage Δ
Debug	68.83% <40.34%> (-0.07%)	⬇️
production	63.34% <35.25%> (-0.08%)	⬇️
test	89.03% <93.93%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/Microsoft.ML.GenAI.Core/Module/GenAILinear.cs	100.00% <ø> (ø)
...icrosoft.ML.GenAI.Core/Module/NewGELUActivation.cs	27.27% <ø> (ø)
.../Microsoft.ML.GenAI.Core/Module/QuantizedLinear.cs	92.24% <ø> (ø)
src/Microsoft.ML.GenAI.Core/Module/RMSNorm.cs	40.00% <100.00%> (ø)
...c/Microsoft.ML.GenAI.LLaMA/LlamaTokenizerHelper.cs	100.00% <100.00%> (ø)
src/Microsoft.ML.GenAI.Phi/Module/Phi2Attention.cs	32.09% <ø> (ø)
src/Microsoft.ML.GenAI.Phi/Module/Phi2MLP.cs	54.54% <ø> (ø)
src/Microsoft.ML.GenAI.Phi/Module/Phi3MLP.cs	55.55% <100.00%> (ø)
...ML.GenAI.Phi/Module/Phi3SuScaledRotaryEmbedding.cs	24.39% <ø> (ø)
...enAI.Phi/Phi3/Phi3CausalLMChatCompletionService.cs	65.00% <100.00%> (ø)
... and 23 more

... and 8 files with indirect coverage changes