CP-17047 logger trace

[niden]

Hello!

• Type: new feature
• Link to issue: NFR: Add trace() logging method and TRACE constant to Logger #17047

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I have updated the relevant CHANGELOG
• I have created a PR for the documentation about this change

Added a trace() method to Phalcon\Logger\Logger together with a new TRACE log level (value 9, label trace) on Phalcon\Logger\Enum and Phalcon\Logger\AbstractLogger. trace() is opt-in: the default threshold stays CUSTOM (8), so trace messages are emitted only after setLogLevel(Enum::TRACE). The existing CUSTOM level and its custom label (the unknown-level bucket) are unchanged.

Thanks