go/runtime/client: Fail SubmitTx early for unsupported runtimes

[kostko]

Fixes #4202

Make sure that the runtime is actually among the supported runtimes as
otherwise we will not be able to actually get any results back.

[codecov]

Codecov Report

Merging #4204 (0bdb984) into master (33aeee6) will decrease coverage by 0.60%.
The diff coverage is 0.00%.

❗ Current head 0bdb984 differs from pull request most recent head 5384f06. Consider uploading reports for the commit 5384f06 to get more accurate results

@@            Coverage Diff             @@
##           master    #4204      +/-   ##
==========================================
- Coverage   69.35%   68.75%   -0.61%     
==========================================
  Files         411      411              
  Lines       47420    47422       +2     
==========================================
- Hits        32887    32603     -284     
- Misses      10498    10793     +295     
+ Partials     4035     4026       -9     

Impacted Files	Coverage Δ
go/runtime/client/client.go	67.29% <0.00%> (-0.37%)	⬇️
...nsensus/tendermint/apps/keymanager/transactions.go	0.00% <0.00%> (-52.95%)	⬇️
go/ias/http/http.go	20.33% <0.00%> (-44.07%)	⬇️
go/oasis-node/cmd/common/metrics/disk.go	65.51% <0.00%> (-20.69%)	⬇️
go/keymanager/api/policy_sgx.go	33.33% <0.00%> (-13.34%)	⬇️
go/runtime/host/sandbox/sandbox.go	71.06% <0.00%> (-10.63%)	⬇️
go/oasis-node/cmd/common/metrics/resource.go	84.00% <0.00%> (-8.00%)	⬇️
go/consensus/tendermint/abci/state/state.go	61.53% <0.00%> (-7.70%)	⬇️
go/consensus/tendermint/apps/staking/auth.go	77.77% <0.00%> (-7.41%)	⬇️
go/oasis-node/cmd/ias/auth.go	68.96% <0.00%> (-6.90%)	⬇️
... and 44 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 33aeee6...5384f06. Read the comment docs.