[configgrpc] Make TCP the default transport type

[evan-bradley]

Description

Most gRPC servers are serving over HTTP/2, so use TCP as the default transport type.

Link to tracking issue

Fixes #13657

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.38%. Comparing base (6db802a) to head (bb3959e).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13673      +/-   ##
==========================================
+ Coverage   91.37%   91.38%   +0.01%     
==========================================
  Files         633      633              
  Lines       39723    39727       +4     
==========================================
+ Hits        36295    36303       +8     
+ Misses       2670     2667       -3     
+ Partials      758      757       -1     

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[bogdandrutu]

Blocking because I fail to understand how http2 implies TCP.

[jade-guiton-dd]

The HTTP/2 protocol is based on TCP. Maybe you're thinking of HTTP/3, which abandoned it in favor of UDP?

[bogdandrutu]

The HTTP/2 protocol is based on TCP. Maybe you're thinking of HTTP/3, which abandoned it in favor of UDP?

It is a bit subtle than that, because HTTP/2 can also be configured to use UDS which is not really TCP, so this is not always true.

Also, Gemini answered:

Yes, HTTP/2 typically relies on TCP as its underlying transport protocol. While HTTP/2 can technically
function without TLS (which uses TCP), it's not the standard practice for external traffic. In most cases,
HTTP/2 utilizes TCP for its connection-based and reliable data transfer characteristics. 

[evan-bradley]

@bogdandrutu I reworded the comment to instead say that we want to listen over the network in most cases.

Reason for blocking fixed