build: use Deno to transpile ext/ TS code

[bartlomieju]

An experiment where we use Deno and [ts-blank-space](https://github.com/bloomberg/ts-blank-space] to transpile ext/ crates, instead of using SWC.

This effectively makes Deno bootstrap itself and should help with compile times - we will no longer need to build SWC in build scripts to transpile sources.

This requires to rewrite some of the internal TS code to avoid limitations from https://github.com/bloomberg/ts-blank-space/blob/main/docs/unsupported_syntax.md, but has an added benefit that the extension code will map to proper places in the stack traces.

[Copilot]

Pull Request Overview

This PR refactors the telemetry module to support transpilation using ts-blank-space by converting TypeScript-specific syntax to JavaScript-compatible alternatives. The changes enable the code to be transpiled without unsupported TypeScript features.

• Converts TypeScript enum declarations to const objects with type aliases using the as const pattern
• Replaces private class members using underscore prefix convention with native JavaScript private fields (# syntax)
• Adds a transpilation tool that validates the TypeScript code can be processed by ts-blank-space

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tools/transpile_ext.js	New transpilation tool that validates telemetry.ts can be processed by ts-blank-space
ext/telemetry/telemetry.ts	Converts 4 enums to const objects, refactors NonRecordingSpan and TraceStateClass to use private fields

Comments suppressed due to low confidence (1)

ext/telemetry/telemetry.ts:1529

• Superfluous argument passed to constructor of class NonRecordingSpan.

    return context.setValue(SPAN_KEY, new NonRecordingSpan(spanContext));

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