…entry#133)

…etsentry#134)

The debug ID field on all source maps is now **serialized as `debugId` rather than `debug_id`**.

To maintain backwards-compatibility with source maps that contain a `debug_id` field, we can still read the `debug_id` field. If a source map contains a `debugId` field and a `debug_id` field, **the `debugId` field takes precedence, which is a change from the old behavior**. 

Corresponding Sentry CLI PR: getsentry/sentry-cli#3005

Closes getsentry#96 
Closes [CLI-240](https://linear.app/getsentry/issue/CLI-240/turn-debug-id-field-to-debugid)

)

* fix: Correct UTF-8 boundary handling in strip_identifier

* test: Replace Japanese with Chinese in CJK test
Change "変数名" (Japanese) to "变量名" (Chinese) for better CJK coverage.

* Reformat the Korean identifier test assertion to improve readability
by breaking it across multiple lines.