fix: ignore case when matching function name

[notauserx]

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Summary

Update logic to search by the lowercase of func_name. Uses unicode crate to facilitate searching function name ignoring case

fixes: #16737

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):

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This change is 

[TCeason]

LGTM

[notauserx]

Does it make sense to add ignore case search in is_builtin_function(func_name) as well?

[andylokandy]

what about handling case here?

Suggested change

	let func_name = func_name.as_str();
	let func_name = func_name.to_lowercase();

[notauserx]

Good suggestion.

Since sugar and built-in functions are matched ignoring case, that's why I created a sep function and moved the logic inside there, and we could do the same in is_builtin_function, otherwise each caller has to convert to lower case before calling the functions

[andylokandy]

Ok. I see. Then I'll suggest replacing &str in all_sugar_functions and builtin_functions to https://crates.io/crates/unicase

[notauserx]

I've used the Ascii type from the unicase crate, a case-insensitive wrapper for ASCII strings. Is this assumption correct? If not, I can switch to the UniCase type, which provides a case-insensitive wrapper for general strings.

[sundy-li]

Let's add a test in name_hit.test to cover the issue.

[notauserx]

Let's add a test in name_hit.test to cover the issue.

Added a test