Compress envelopes in server SDKs with `zstd`, falling back to `gzip`

[logaretm]

@sentry/node / @sentry/node-core already gzip envelopes >32 KB (packages/node-core/src/transports/http.ts)

zstd is a better compression algorithm which is supported by Relay and is available on all major runtimes today, but support is relatively new:

Runtime	Version	Release date	Evidence
Node.js	v22.15.0 (LTS) / v23.8.0	~Jan 2025	nodejs.org/api/zlib.html
Bun	v1.2.14	~May 2025	oven-sh/bun#23095, #20313
Deno	v2.6.9 / v2.7.0	Feb 10 / Feb 25, 2026	denoland/deno#32025
Cloudflare Workers	workerd merge Feb 19, 2026	~Feb–Mar 2026 rollout (requires nodejs_compat flag)	cloudflare/workerd#6117

The API offers better compression ratios which can be used on smaller than 32kb payloads we have today and offer better gains and less load to our users and our servers.

API is mainly available through node:zlib's createZstdCompress function. Worth noting that it is marked as experimental and on the time of writing this issue can be too new.

Seems its going to be used by our CLI getsentry/cli#843

[linear-code]

JS-2278