[docs]Refine ConfigOptionsDocGenerator and fix MDX formatting

[Prajwal-banakar]

Purpose

Linked issue: close #2586

The purpose of this change is to enhance the ConfigOptionsDocGenerator to produce cleaner, more professional MDX documentation. It fixes several formatting artifacts in the auto-generated configuration files, such as Table to list, incorrect type rendering and unformatted description placeholders, and improves the overall code quality of the generator itself.

Brief change log

Changed table to list format for better readability

Enhanced Type Formatting: Refined the getType() logic to strip trailing generic brackets (e.g., converting String> to String) and normalized common Java types for documentation.

Improved Descriptions: Updated cleanDescription() to replace %s placeholders with true to ensure generated sentences are grammatically complete and readable.

Refined Scoping: Improved the logic for the "Scope" field to correctly categorize configurations as Client, Table, or Server based on their key prefixes.

Code Quality & Checkstyle: * Fixed "ignored return value" warnings for File.mkdirs().

Optimized imports and resolved reflective access warnings for the Internal annotation.

Decoupled the generator from ConfigDocUtils to ensure it can run as a standalone utility without classpath resolution issues.

Tests

Manually verified by running the ConfigOptionsDocGenerator main method and inspecting the resulting _partial_config.mdx file.

Verified that the generated MDX renders correctly in a Markdown previewer with working anchors and valid formatting.

Ran ./mvnw compile -pl fluss-docgen -am it passed perfectly

API and Format

This change does not affect the Fluss runtime API or storage format. It only affects the internal documentation generation tool and the resulting .mdx files.

Documentation

This PR improves the quality of the existing configuration documentation. No new user-facing features were added.

[Prajwal-banakar]

Hi @wuchong,

I've addressed your feedback from the previous PR ( #2474 ) and continued the work here to fulfill the requirements mentioned in your #2474 (comment). I haven't removed the manual tables yet as I'm waiting for your feedback on the automated generation first!

[wuchong]

Thank you @Prajwal-banakar , I will continue to review this after 0.9 RC1 is out. Busy preparing the release.

[Prajwal-banakar]

Hi Jark! Totally understand, Congratulations to the team on reaching this milestone! good luck with the 0.9 RC1 release.