feat(gateway): support TCP routes

[michaelbeaumont]

Summary

Closes #3944

• Assumes backend services for a TCP route are TCP if not marked.

[codecov-commenter]

Codecov Report

Merging #4470 (3f6a26a) into master (915ad01) will increase coverage by 0.05%.
The diff coverage is 53.93%.

@@            Coverage Diff             @@
##           master    #4470      +/-   ##
==========================================
+ Coverage   55.50%   55.55%   +0.05%     
==========================================
  Files         946      946              
  Lines       58223    58344     +121     
==========================================
+ Hits        32315    32415     +100     
- Misses      23370    23391      +21     
  Partials     2538     2538              

Impacted Files	Coverage Δ
...ore/resources/apis/mesh/gateway_route_validator.go	97.33% <ø> (+1.28%)	⬆️
pkg/core/resources/apis/mesh/gateway_validator.go	83.67% <ø> (ø)
pkg/plugins/runtime/gateway/route/table.go	100.00% <ø> (ø)
...kg/xds/envoy/listeners/filter_chain_configurers.go	97.43% <ø> (ø)
test/framework/client/collect.go	0.00% <0.00%> (ø)
...est/framework/deployments/testserver/deployment.go	0.00% <0.00%> (ø)
...est/framework/deployments/testserver/kubernetes.go	0.00% <0.00%> (ø)
test/framework/exec_util.go	0.00% <ø> (ø)
...s/runtime/gateway/route_configuration_generator.go	80.00% <50.00%> (-20.00%)	⬇️
pkg/plugins/runtime/gateway/generator.go	85.91% <86.66%> (-0.16%)	⬇️
... and 15 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 915ad01...3f6a26a. Read the comment docs.

[jakubdyszkiewicz]

nice!