esm: avoid super-linear data URL MIME regex

[skdas20]

Fixes: #61904

This updates ESM data URL MIME extraction regexes to remove overlapping quantifiers that allow super-linear backtracking.

• Replaced (?:[^,]*?)(;base64)?, with (?:;[^,]*)?, in:
  • lib/internal/modules/esm/get_format.js
  • lib/internal/modules/esm/load.js

Behavior is preserved for existing valid/invalid data: URL shapes while avoiding pathological backtracking on crafted inputs.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[jsumners-nr]

Where are tests to assert the undesired behavior is resolved by the changes?

[skdas20]

Added regression coverage in test/parallel/test-esm-data-url-format-regex-backtracking.js (commit 740d1320).

The test exercises defaultGetFormat() with a long malformed data: URL (data:a/aaaa...B) that used to trigger super-linear backtracking, and asserts the path now completes within a platform-adjusted bound.