builtins: create function to aggregate aggregated stmt metadata

[xinhaoz]

server: prefer string concat over str format where possible

A number of places in the combined stats api were using string
format where a string concatenation would have worked.

Release note: None

Epic: none

server: format sql activity queries

Reformat queries for consistency and readability.

Epic: none

Release note: None

builtins: create function to aggregate aggregated stmt metadata

The statement activity table used to cache aggregated stmt stats for the sql activity page stores aggregated metadata. Previously we used the same query as the one used for system.statement_statistics, which stores unaggregated metadata, on the activity table. Using the aggregate function for unaggregated metadata on aggregated metadata was nto valid, leading to incorrect JSON fields being produced. This commit introduces the builtin crdb_internal.combine_aggregated_stmt_metadata which can be used to correctly aggregate the metadata column on the stmt activity table.

Fixes: #103895

Release note (bug fix): On the UI, selecting a database filter from the filters menu in the sql activity page should function as expected. This fixes a preivous bug where the filter would break and not show any results when the results were retrieved from the stmt activity table instead of the persisted table.

[cockroach-teamcity]

This change is 

[maryliag]

Your PR has 3 commits, so on the PR description add more information about the changes on the other 2 commits.

Reviewed 1 of 1 files at r1, 1 of 1 files at r2, 5 of 5 files at r3.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @xinhaoz)

---

pkg/server/combined_statement_stats.go line 1513 at r3 (raw file):

	// We will have 1 open iterator at a time. For the deferred close operation, we will
	// only close the iterator if there were no errors creating the iterator. Closing an
	// iterator that returned an error on creation will cause a nil pointer deref.

nit: defer

[xinhaoz]

TFTR!
bors r+

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

---

error creating merge commit from 68c6390 to blathers/backport-release-23.1-105351: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 23.1.x failed. See errors above.

---

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}