Documentation: logs of a single request

[mnapoli]

A new "Logs of a single request" section in environment/logs.mdx:

• Bref's Monolog formatter starts every log line with the request ID of the invocation
• in Bref Cloud: click the request ID of a log line to see all the logs of the request, and the X-Ray trace of a request shows its logs (screenshot)
• from the terminal: bref logs --search=<id> --all, the first 8 characters of the ID are enough
• in CloudWatch Logs Insights: filter @requestId = '<id>'
• with another formatter: a Monolog processor reading $_SERVER['LAMBDA_REQUEST_ID']

Split from #2189 (PHP-FPM receives LAMBDA_REQUEST_ID).

To merge once these are out, since the page describes them:

• Start log lines with the Lambda request ID monolog-bridge#2, released as bref/monolog-bridge 2.0 (the request ID at the start of each line)
• brefphp/cloud#392 deployed (the request IDs in the log viewer and the logs of a trace)