feat(core): export native bridge utility functions

[sahilsharda]

Title: feat(core): export native bridge utility functions

Description

This PR exports the isRelativeOrProxyUrl and createProxyUrl utility functions from the native bridge, making them accessible via the Capacitor global object. This addresses existing TODOs in the codebase and allows plugins to better handle Capacitor-proxied URLs.

Changes

• Updated CapacitorInstance interface in core/src/definitions-internal.ts
• Exported functions in core/native-bridge.ts
• Removed TODO comments

Verification

• Ran npm run build:nativebridge to ensure successful build
• Ran npm test to ensure no regressions (All tests passed)

Closes #8255