server(ticdc): use TiDB gcTuner in a more reasonable way (#9786)

[ti-chi-bot]

This is an automated cherry-pick of #9786

What problem does this PR solve?

Issue Number: close #9762

What is changed and how it works?

1. disable gc tunner by default
2. if server memory size is greater than 512G, disable gc tuner

Check List

Tests

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

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

disable gc tuner by default

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sdojjy

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[sdojjy]

/retest-required

[sdojjy]

/retest-required