Auto-inject `sentry-label` from static JSX text children in Babel plugin

[antonis]

Extend @sentry/babel-plugin-component-annotate to auto-emit a sentry-label prop from static JSX text children at build time, so devs get meaningful labels without writing the prop by hand.

Example transform:

// Before
<TouchableOpacity onPress={save}>
  <Text>Save workout</Text>
</TouchableOpacity>

// After (at build time)
<TouchableOpacity sentry-label="Save workout" onPress={save}>
  <Text>Save workout</Text>
</TouchableOpacity>

The SDK already reads sentry-label via getLabelValue in touchevents.tsx:325 — no SDK-side change needed.

Constraints:

• Only static string literals — <Text>{dynamicVar}</Text> gets nothing
• Skip if sentry-label is already present (user-authored wins)
• Cap at ~64 chars
• Same plugin is used by web JS SDK — confirm no unintended side effects there

Scope: Change is in getsentry/sentry-javascript-bundler-plugins repo, not this one. Babel AST visitor addition.

[linear-code]

RN-609