fix(logs): Add support for msg in pino integration

[chargome]

This fix will check for a msg field in the logger call (https://getpino.io/#/docs/api?id=messagekey-string) if there was no message string passed:

logger.info("This was always logged");
logger.info({ msg: "This now gets logged too" }); // This pr adds support for this

closes #18381
closes https://linear.app/getsentry/issue/JS-1245/pinotransport-ignores-msg-field

[linear]

JS-1245 pinoTransport ignores "msg" field

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.
⚠️ Warning: Base artifact is not the latest one, because the latest workflow run is not done yet. This may lead to incorrect results. Try to re-run all tests to get up to date results.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,967	-	8,876	+1%
GET With Sentry	1,669	19%	1,739	-4%
GET With Sentry (error only)	5,930	66%	6,212	-5%
POST Baseline	1,183	-	1,210	-2%
POST With Sentry	587	50%	603	-3%
POST With Sentry (error only)	1,039	88%	1,083	-4%
MYSQL Baseline	3,270	-	3,321	-2%
MYSQL With Sentry	394	12%	524	-25%
MYSQL With Sentry (error only)	2,669	82%	2,731	-2%

View base workflow run