Change RefSet and RefMap to use actually private class fields

[Snuffleupagus]

Slightly smaller diff with https://github.com/mozilla/pdf.js/pull/21728/changes?w=1

[codecov-commenter]

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.10%. Comparing base (99df11c) to head (edd5242).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/core/primitives.js	95.65%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21728      +/-   ##
==========================================
+ Coverage   90.08%   90.10%   +0.01%     
==========================================
  Files         264      264              
  Lines       67191    67194       +3     
==========================================
+ Hits        60532    60542      +10     
+ Misses       6659     6652       -7     

Flag	Coverage Δ
browsertest	66.42% <95.65%> (+0.02%)	⬆️
fonttest	8.99% <0.00%> (-0.01%)	⬇️
integrationtest	69.28% <86.95%> (-0.01%)	⬇️
unittest	58.28% <95.65%> (+0.02%)	⬆️
unittestcli	56.63% <95.65%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Snuffleupagus]

/botio browsertest

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.241.84.105:8877/a50247577f9f7c5/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.193.163.58:8877/678357c6ac2f88f/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.241.84.105:8877/a50247577f9f7c5/output.txt

Total script time: 16.54 mins

• Regression tests: Passed

[moz-tools-bot]

From: Bot.io (Windows)

---

Success

Full output at http://54.193.163.58:8877/678357c6ac2f88f/output.txt

Total script time: 23.54 mins

• Regression tests: Passed