feat: increase GRPC REQUEST_TIMEOUT to 15 seconds and add comment

[gaius-qi]

Description

This pull request includes updates to the Cargo.toml file to bump the version of multiple dependencies and the package itself, as well as a change to the REQUEST_TIMEOUT constant in the grpc module to extend the timeout duration and provide additional documentation.

Dependency and version updates:

• Updated the package version in Cargo.toml from 0.2.28 to 0.2.29.
• Updated the versions of several workspace dependencies (dragonfly-client, dragonfly-client-core, dragonfly-client-config, etc.) in Cargo.toml from 0.2.28 to 0.2.29.

Timeout configuration changes:

• Increased the REQUEST_TIMEOUT constant in dragonfly-client/src/grpc/mod.rs from 5 seconds to 15 seconds and added detailed documentation explaining its purpose and relation to scheduler configuration.

Related Issue

Motivation and Context

Screenshots (if appropriate)

[Liam-Zhao]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.45%. Comparing base (604a945) to head (9b6c127).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1150      +/-   ##
==========================================
- Coverage   49.51%   49.45%   -0.06%     
==========================================
  Files          58       58              
  Lines       12085    12085              
==========================================
- Hits         5984     5977       -7     
- Misses       6101     6108       +7     

Files with missing lines	Coverage Δ
dragonfly-client/src/grpc/mod.rs	0.00% <ø> (ø)

... and 1 file with indirect coverage changes

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