backport crdb 98422 GetConfReader freshness check - #75

control: job assigned to worker 01KX4DEYP6QDEG7J6RQJ9315JP [factory aws, i-0c91b5a6a193769c1] (queued for 32 s)
...
task: starting task 0: "setup"
task: process exited: duration 19523 ms, exit code 0
...
task: starting task 1: "authentication"
task: process exited: duration 9 ms, exit code 0
...
task: starting task 2: "clone repository"
task: process exited: duration 31397 ms, exit code 0
...
task: starting task 3: "build"
...
| ?   github.com/cockroachdb/cockroach/pkg/sql/opt/exec[no test files]
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/exec/execbuilder43.387s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/exec/explain0.326s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/idxconstraint0.156s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/indexrec0.247s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/invertedexpr0.154s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/invertedidx0.215s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/memo1.983s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/norm1.146s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/opbench0.951s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/optbuilder0.807s
| ?   github.com/cockroachdb/cockroach/pkg/sql/opt/optgen/cmd/langgen[no test files]
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/optgen/cmd/optfmt0.062s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/optgen/cmd/optgen0.060s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/optgen/exprgen0.085s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/optgen/lang0.085s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/ordering0.103s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/partialidx0.110s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/partition0.122s
| ok  github.com/cockroachdb/cockroach/pkg/sql/opt/props0.354s