feat: implement PreheatFile and StatFile for scheduler (#4380)

[EvanCley]

Description

for scheduler rpc api, add PreheatFile and StatFile, which call listTaskEntries and downloadTask of dfdaemon client to complete preheat

Related Issue

#4380

Motivation and Context

for files on storage like oss, hdfs .etc, it also need preheat to accelerate download. This commit focus on exposing PreheatFile and StatFile on scheduler to be called

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

❌ Patch coverage is 69.72112% with 76 lines in your changes missing coverage. Please review.
✅ Project coverage is 32.93%. Comparing base (3b981e9) to head (0b80899).
⚠️ Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
scheduler/job/job.go	0.00%	37 Missing ⚠️
scheduler/service/service_v2.go	89.53%	13 Missing and 5 partials ⚠️
scheduler/rpcserver/scheduler_server_v2.go	0.00%	16 Missing ⚠️
pkg/rpc/dfdaemon/client/client_v2.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4381      +/-   ##
==========================================
+ Coverage   32.73%   32.93%   +0.19%     
==========================================
  Files         350      350              
  Lines       41632    41868     +236     
==========================================
+ Hits        13630    13789     +159     
- Misses      27112    27184      +72     
- Partials      890      895       +5     

Flag	Coverage Δ
unittests	32.93% <69.72%> (+0.19%)	⬆️

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

Files with missing lines	Coverage Δ
internal/dflog/logger.go	57.36% <100.00%> (+2.07%)	⬆️
scheduler/job/mocks/job_mock.go	89.47% <100.00%> (+1.97%)	⬆️
scheduler/metrics/metrics.go	10.89% <ø> (ø)
pkg/rpc/dfdaemon/client/client_v2.go	0.00% <0.00%> (ø)
scheduler/rpcserver/scheduler_server_v2.go	0.97% <0.00%> (-0.08%)	⬇️
scheduler/service/service_v2.go	52.81% <89.53%> (+2.67%)	⬆️
scheduler/job/job.go	0.00% <0.00%> (ø)

... and 6 files with indirect coverage changes

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[gaius-qi]

LGTM

[chlins]

lgtm