[DIOPI] Wx/align standard flash attention interface definition

[POI-WX]

Motivation and Context

• Align standard flash attention interface definition.
• Add implementation of diopiFlashAttention and diopiFlashAttentionVarLen for camb.
• Add implementation of diopiCustomizedFlashAttention and diopiCustomizedFlashAttentionVarLen for ascend.

Description

Use cases (Optional)

BC-breaking (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the Contributors.md to create this PR.
• Pre-commit or linting tools indicated in Contributors.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.