feat: Disable string truncation for events by default

[alexander-alderman-webb]

Description

Remove the default string limit applied when serializing envelopes by changing
max_value_length to default to None. Settingmax_value_length to None disables string truncation.

This follows the earlier limit increase in #4632.

Replace DEFAULT_MAX_VALUE_LENGTH with the value 1024 in tests, which was the original limit.

Issues

Closes SDK-1246

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[linear-code]

SDK-1246

[github-actions]

Codecov Results 📊

✅ 282 passed | Total: 282 | Pass Rate: 100% | Execution Time: 45.88s

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

❌ Patch coverage is 66.67%. Project has 14857 uncovered lines.
❌ Project coverage is 33.5%. Comparing base (base) to head (head).

Files with missing lines (3)

File	Patch %	Lines
utils.py	51.50%	⚠️ 454 Missing and 81 partials
serializer.py	86.02%	⚠️ 26 Missing and 11 partials
consts.py	99.50%	⚠️ 2 Missing

Coverage diff

@@ Coverage Diff @@## main #PR +/-##
==========================================
- Coverage 33.53% 33.50% -0.03%
==========================================
Files 190 190 —
Lines 22342 22340 -2
Branches 7576 7574 -2
==========================================
+ Hits 7492 7483 -9- Misses 14850 14857 +7- Partials 749 748 -1

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Generated by Codecov Action

[sentrivana]

Please make sure to call this out in the changelog and let people know how to mitigate if they run into trouble (max_value_length)