util: only set rlimit if needed

[cce]

Summary

We don't need to lower the current RLIMIT_NOFILE limit, which we were doing before. This ensures that we only raise it if needed. It also adds a constant number of additional FDs to the requested limit if P2P is enabled. This constant is arbitrary, we could decide to adjust it, or make it a separate configuration value.

Test Plan

Existing tests should pass.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 51.61%. Comparing base (5b9eee2) to head (3259737).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
util/util.go	0.00%	9 Missing ⚠️
daemon/algod/server.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6289      +/-   ##
==========================================
- Coverage   51.62%   51.61%   -0.02%     
==========================================
  Files         647      647              
  Lines       86882    86893      +11     
==========================================
- Hits        44855    44847       -8     
- Misses      39166    39182      +16     
- Partials     2861     2864       +3     

☔ View full report in Codecov by Sentry.
📢 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.

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.