log: add support for decoding JSON logs

[exalate-issue-sync[bot]]

Exalate commented:

Previously, our logging code did not have the ability to recognize and decode JSON formatted log files. This led to problems when retrieving logs via API endpoints and when running commands such as merge-logs to process logs from debug.zip files.

This commit adds support for the json, json-compact, json-fluent, and json-fluent-compact formats via one generalized JSON decoder.

Resolves #66684

Release note (ops change, cli change): debug zip and merge-logs commands will now work with JSON formatted logs.

Jira issue: CRDB-14742

Jira Issue: DOC-3143

Jira Issue: DOC-3617

[exalate-issue-sync[bot]]

Exalate commented:

             cockroach-teamcity commented:

This change is 

[exalate-issue-sync[bot]]

Exalate commented: WARNING: Comments will be synced to GitHub!

Do not include sensitive information.

GitHub issue (#79356):

• https://github.com/cockroachdb/docs/issues/79356

WARNING: Comments will be synced to GitHub!