feat: add user and privilege proto definition

[yezizp2012]

What's changed and what's your intention?

As title, according to #2643

Please explain IN DETAIL what the changes are in this PR and why they are needed:

• Summarize your change (mandatory)
• How does this PR work? Need a brief introduction for the changed logic (optional)
• Describe clearly one logical change and avoid lazy messages (optional)
• Describe any limitations of the current code (optional)

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

Part of #2193

[codecov]

Codecov Report

Merging #2645 (2dd8ffa) into main (f2c003f) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2645   +/-   ##
=======================================
  Coverage   72.19%   72.19%           
=======================================
  Files         681      681           
  Lines       88477    88494   +17     
=======================================
+ Hits        63872    63888   +16     
- Misses      24605    24606    +1     

Flag	Coverage Δ
rust	72.19% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/prost/src/lib.rs	96.29% <ø> (ø)
src/utils/pgwire/src/pg_protocol.rs	0.00% <0.00%> (ø)
src/risedevtool/src/config_gen/grafana_gen.rs	0.00% <0.00%> (ø)
src/utils/pgwire/src/pg_message.rs	8.08% <0.00%> (+8.08%)	⬆️

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[neverchanje]

Do we have a plan for what SQL we want to support specifically? There are several options in Postgres's CREATE USER command, https://www.postgresql.org/docs/current/sql-createuser.html. I think we need a priority and focus on delivering a minimized feature set. I don't know what is required in the initial stage.

[yezizp2012]

Do we have a plan for what SQL we want to support specifically? There are several options in Postgres's CREATE USER command, https://www.postgresql.org/docs/current/sql-createuser.html. I think we need a priority and focus on delivering a minimized feature set. I don't know what is required in the initial stage.

Please visit #2643 for more details. I list all syntaxes we plan to support in current stage.