Improve sanitizer approach

#### What problem would the feature you're requesting solve? Please describe.

We need to simplify the class Sanitizer.cs to improve performance. Currently it is using both regex approach and string comparison. We can optimize it to use either of these approaches. Note that the method `Sanitize()` gets executed a lot as it examines the logs and sanitizes any secret related strings. Also, using regex comparison is very expensive. For that we can use .Net feature GeneratedRegex for performance - [link](https://learn.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-source-generators?pivots=dotnet-8-0#source-generation)

Documentation here - [Link](https://microsoft.sharepoint.com/:w:/t/AzureFunctionsCoreTeam/EV09nmZ5_SZJv4tFfxDwpxIB_eamOrLsp2vi8uQujYIGxQ?e=0qmnxz)

Start by reading Sanitizer.cs and the Sanitize() entry point, then review the linked .NET GeneratedRegex documentation and the internal sanitizer design document. Compare the existing regex and string-comparison paths, and consider how the hot path can use one approach while continuing to sanitize secret-related log strings correctly.

Written by the indexing model from the issue text.