refactor: enable setting xline log level using RUST_LOG env

[bsbds]

Please briefly answer these questions:

• what problem are you trying to solve? (or if there's no problem, what's the motivation for this change?)

• what changes does this pull request make?

• are there any non-obvious implications of these changes? (does it break compatibility with previous versions, etc)

[mergify]

@bsbds Convert your pr to draft since CI failed

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 75.18%. Comparing base (e35b35a) to head (a08437c).
Report is 306 commits behind head on master.

Files with missing lines	Patch %	Lines
crates/xline/src/utils/trace.rs	0.00%	5 Missing ⚠️
crates/utils/src/parser.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #989      +/-   ##
==========================================
- Coverage   75.55%   75.18%   -0.37%     
==========================================
  Files         180      189       +9     
  Lines       26938    28395    +1457     
  Branches    26938    28395    +1457     
==========================================
+ Hits        20353    21349     +996     
- Misses       5366     5753     +387     
- Partials     1219     1293      +74     

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