sql: enhance SQL errors + make them reportable

[knz]

This is a sub-issue of #15854 and re-phrases actionable items for 2.1:

• audit the SQL package for errors constructed by other means than using the pgerror constructors; convert any remaining errors accordingly.
• audit the SQL package for "leaf" uses of 3rd-party packages that can generate non-pgerror errors, and add suitable pgerror wrapper. This can be automated with a linter.
• modify the pgerror error constructors so that sensitive and non-sensitive information can be distinguished from each other (defined so that non-annotated info is considered sensitive by default)
• make the data collection by app_stats.go + reporting able to report non-sensitive data
• (main item from log+sql+reporting: enhance the auto reporting of issues #15854): in pgwire detect any remaining non-pgerror errors and convert them to "internal server error" so that users become less surprised.

[knz]

@vivekmenezes this is a work item that is driven by a user story but requires cross-team work at multiple levels (across the entire SQL layer of CockroachDB). So I added it to at least two projects that I think are relevant.

I probably would like to be involved; I think @dt was interested to look into this, and perhaps Bram will be as well.

[knz]

Assigning according to airtable; this assignment may change as the roadmap gets further refined.

[knz]

(still working on this, see #36987)

[knz]

This work has been completed.