update tsh db env/config ux

[GavinFrazar]

stacked on related change for tsh db connect: #30527

This PR changes tsh db env and tsh db config such that when a given db name doesn't match any active cert fully,
it calls the ListDatabases API to check if any inactive databases fully match.

Example UX Diff:

Suppose we have two databases, one a prefix of the other and not logged into:

$ tsh db ls
Name                                      Description                   Allowed Users Labels Connect                  
----------------------------------------- ----------------------------- ------------- ------ ------------------------ 
postgres                                  Example dyn database resource [* alice]                                     
> postgres2 (user: alice, db: postgres... Example dyn database resource [* alice]            tsh db connect postgres2 

Prior behavior: (Note that postgres-2 is used, because "postgres" is a prefix of its name)

$ tsh db env postgres
export PGSSLROOTCERT=/Users/gavin/.tsh/keys/mars.local.gd/cas/mars.local.gd.pem
export PGSSLCERT=/Users/gavin/.tsh/keys/mars.local.gd/martian-db/mars.local.gd/postgres2-x509.pem
export PGDATABASE=postgres
export PGPORT=6543
export PGSSLMODE=verify-full
export PGSSLKEY=/Users/gavin/.tsh/keys/mars.local.gd/martian
export PGUSER=alice
export PGGSSENCMODE=disable
export PGHOST=postgres.mars.local.gd

New behavior:

$ tsh db env postgres
ERROR: not logged into database "postgres"

[public-teleport-github-review-bot]

@GavinFrazar See the table below for backport results.

Branch	Result
branch/v13	Create PR