Storage: (Refactor) Separate bg tasks out

[breezewish]

What problem does this PR solve?

Issue Number: ref #5831

Problem Summary:

What is changed and how it works?

Move bg and gc into a standalone file. This PR does not change any code logic.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hongyunyan
• lidezhu

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[hongyunyan]

LGTM

[breezewish]

/merge

[ti-chi-bot]

@breezewish: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: e774078

[sre-bot]

Coverage for changed files

Filename                           Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DeltaMergeStore.cpp                    925               160    82.70%          48                 2    95.83%        1378               233    83.09%         494               160    67.61%
DeltaMergeStore_InternalBg.cpp         282               210    25.53%          10                 3    70.00%         378               191    49.47%         124                82    33.87%
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                 1207               370    69.35%          58                 5    91.38%        1756               424    75.85%         618               242    60.84%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18717      8124             56.60%    216537  83381        61.49%

full coverage report (for internal network access only)

[JaySon-Huang]

/rebuild

[JaySon-Huang]

/run-integration-test