perf: reduce prebuilt binary size

[IlyasShabi]

What does this PR do?:
Adds size reduction flags to binding.gyp in order to drop debug info, hide symbol visibility, and enable dead-code stripping.

• macOS binaries go from 214,624 B to 184,768 B (−14%).
• Linux and Windows gain from the same flags.
• Across all 63 prebuilds that's roughly 15.5 MB → 13.5 MB.

The symbol table is deliberately kept so crash reports still show function names. Only the export table shrinks, which nothing reads at runtime. Sanitizer builds are excluded.

Motivation:
prebuilds/ is 15.5 MB of the package's size, and every dd-trace-js user downloads it. A chunk of that is debug info and exported symbols nothing uses.

[github-actions]

Overall package size

Self size: 2.61 MB
Deduped: 3.31 MB
No deduping: 3.31 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | pprof-format | 2.3.1 | 504.33 kB | 504.33 kB | | source-map | 0.8.0 | 185.66 kB | 185.66 kB | | node-gyp-build | 4.8.4 | 13.86 kB | 13.86 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[szegedi]

LGTM, and nice reduction.

[szegedi]

Out of curiosity, can we know what dead code is being stripped away? There might be an opportunity to throw it out of source code as well. Of course, if it's not globally dead code but just code that's inactive in particular targets then that's obviously a different story…

[IlyasShabi]

Well keeping the flag is about now and later:

• the last commit removes the one dead signature it surfaced and the rest is the case you guessed (NAN header templates).
• It means any dead code we introduce stops shipping in the binaries automatically.