fix: js-client-sdk bootstrap data parsed 2x

[joker23]

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

sdk-1708

Describe the solution you've provided

• added a new hidden property to BrowserIdentifyOptions to store parsed bootstrap data
• IF that bootstrap data is already parsed, then we will used that instead of reprocessing
• This PR should only affect the initialization flow where we preload the bootstrap data (processing it) so it could be used before client is initialized

---

Note

Prevents duplicate parsing of bootstrap data during initialization and ensures parsed flags are reused across start() and identify().

• Adds hidden bootstrapParsed to BrowserIdentifyOptions; BrowserClient.start() parses once, presets flags, and passes parsed data to BrowserDataManager
• BrowserDataManager consumes bootstrapParsed when available (falls back to parsing), and now updates status using DataSourceState.Initializing
• Tests added: verifies bootstrap parsed exactly once and that subsequent identify() with new bootstrap data replaces flag values

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[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25394 bytes
Compressed size limit: 26000
Uncompressed size: 124693 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 18984 bytes
Compressed size limit: 20000
Uncompressed size: 98086 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 171466 bytes
Compressed size limit: 200000
Uncompressed size: 798155 bytes

[joker23]

Sneaking this in if reviewers don't mind... End value is the same, but looks better this way imo

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 23331 bytes
Compressed size limit: 25000
Uncompressed size: 81050 bytes