Refactor/better debug

[Phoenix500526]

Please briefly answer these questions:
Currently, some gRPC requests and responses consist of bytes and are not human-readable. I implemented the Display trait for these requests and responses so they can be output in a more developer-friendly format. The reason for implementing Display instead of Debug is that Prost automatically derives Debug for all requests and responses. This pr can reduce the log content size which mentioned in issue #516 .

• what problem are you trying to solve? (or if there's no problem, what's the motivation for this change?)
  Implement Display trait for some requests and responses

• what changes does this pull request make?

• are there any non-obvious implications of these changes? (does it break compatibility with previous versions, etc)
  no

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 238 lines in your changes are missing coverage. Please review.

Project coverage is 74.48%. Comparing base (0709eea) to head (dafdb54).
Report is 9 commits behind head on master.

Files	Patch %	Lines
crates/xlineapi/src/lib.rs	0.00%	214 Missing ⚠️
crates/xline/src/server/auth_server.rs	0.00%	9 Missing ⚠️
crates/xline/src/storage/kvwatcher.rs	0.00%	8 Missing ⚠️
crates/xline/src/server/kv_server.rs	0.00%	4 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #683      +/-   ##
==========================================
- Coverage   74.74%   74.48%   -0.27%     
==========================================
  Files         172      173       +1     
  Lines       25374    25871     +497     
  Branches    25374    25871     +497     
==========================================
+ Hits        18966    19270     +304     
- Misses       5219     5399     +180     
- Partials     1189     1202      +13     

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