Change tsdump default format to raw

**Is your feature request related to a problem? Please describe.**
Since CRL internal tools prefer to use raw format to analyze tsdump, this GH issue is to request changing the default format from text to raw. It'll generate the format w/o specifying the `--format=raw` parameter.
It's discussed w/ Eng on https://cockroachlabs.slack.com/archives/C063CP41TG9/p1747690182114679

**Additional context**
Add any other context or screenshots about the feature request here.
With the current default=text, users need to specify `--format=raw` parameter everytime.

Jira issue: CRDB-50891

Start by locating the tsdump entry point and the handling of the --format parameter. Confirm the current default is text, then update the default to raw and verify the behavior with the project's relevant tests or command checks.

Written by the indexing model from the issue text.