release-21.2: ui/cluster-ui: fix routing to statement details page

[xinhaoz]

Backport 1/1 commits from #70600.

/cc @cockroachdb/release

---

Partially addresses #68843

Previously, we used two different bases for the statement details page, which
depended on which route parameters were included. /statements/ was used when
the app name was included in the path, and otherwise /statement/ was used.
The database name was also optionally included in the path name, further
complicating routing to the statement details page as these optional route
params lead to the need to include all combinations of route parameters for
statement detail paths,

This commit turns all optional route parameters into query string parameters,
removing the necessity for different base paths and route param combinations.

Release note (ui change): For statement detail URLs, the app name and database
name are now query string parameters. The route to statement details is
now definitively /statement/:implicitTxn/:statement?{queryStringParams}.

e.g.
statement/true/SELECT%20city%2C%20id%20FROM%20vehicles%20WHERE%20city%20%3D%20%241?database=movr&app=movr

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[maryliag]

Make sure the tests are passing and then

Reviewable status: complete! 1 of 0 LGTMs obtained