build: enable -fvisibility to improve startup speeds

[avivkeller]

cc @joyeecheung this resolves your TODO(joyeecheung): investigate if it breaks addons. comment.

If I understand correctly, this is fine to enable, since:

• All addon test suites pass against the build (on my mac)
• The removed strong symbols are declared only in internal headers under an internal namespace used only internslly. (With the addition of signo_string). Weak symbols don't matter here.

Plus, it speeds up startups by ~33% (yay!):

Running JS (--eval)

$ hyperfine --warmup 30 --runs 60 'node -e 0' './node -e 0'

Benchmark 1: node -e 0
  Time (mean ± σ):      61.6 ms ±  11.9 ms    [User:42.7 ms, System: 12.8 ms]
  Range (min … max):    45.9 ms … 108.5 ms    60 runs
 
Benchmark 2: ./node -e 0
  Time (mean ± σ):      45.4 ms ±   8.7 ms    [User:29.3 ms, System: 12.2 ms]
  Range (min … max):    31.2 ms …  79.3 ms    60 runs
 
Summary
  ./node -e 0 ran
    1.36 ± 0.37 times faster than node -e 0

--version Only

$ hyperfine --warmup 30 --runs 60 'node --version' './node --version'

Benchmark 1: node --version
  Time (mean ± σ):      36.9 ms ±  10.8 ms    [User:25.1 ms, System: 7.0 ms]
  Range (min … max):    25.7 ms …  83.5 ms    60 runs
 
Benchmark 2: ./node --version
  Time (mean ± σ):      23.6 ms ±  10.5 ms    [User:11.3 ms, System: 6.2 ms]
  Range (min … max):    11.0 ms …  65.4 ms    60 runs
 
Summary
  ./node --version ran
    1.56 ± 0.84 times faster than node --version

[nodejs-github-bot]

Review requested:

• @nodejs/gyp
• @nodejs/security-wg
• @nodejs/url
• @nodejs/v8-update

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.14%. Comparing base (18eaa73) to head (349d171).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #65526   +/-   ##
=======================================
  Coverage   90.13%   90.14%           
=======================================
  Files         751      751           
  Lines      253656   253679   +23     
  Branches    47787    47788    +1     
=======================================
+ Hits       228631   228668   +37     
- Misses      16258    16266    +8     
+ Partials     8767     8745   -22     

Files with missing lines	Coverage Δ
src/node.h	92.30% <ø> (ø)

... and 33 files with indirect coverage changes

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