Add flag & toml config for gRPC server

[amaury1093]

Description

Add flag & toml config for gRPC server

ref: #5921 (comment)

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #6933 into master will increase coverage by 5.42%.
The diff coverage is 56.41%.

@@            Coverage Diff             @@
##           master    #6933      +/-   ##
==========================================
+ Coverage   55.60%   61.02%   +5.42%     
==========================================
  Files         457      379      -78     
  Lines       27440    24640    -2800     
==========================================
- Hits        15257    15037     -220     
+ Misses      11083     8430    -2653     
- Partials     1100     1173      +73     

[fedekunze]

we need to expose the new port to the nodes on docker. The following files need to be updated

• docker-compose.yml
• Dockerfile

[amaury1093]

let me fix the failing test first before merging