Add knobs for min/max Ratekeeper limit

[jzhou77]

The default has no effects. These knobs can be used in emergency situations with care.

20220808-220133-jzhou-f120af8ec66619d7

Manually updated the knob value and verified RkUpdate events have the limit in effect.

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[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: e933ac6
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: e933ac6
• Duration 1:06:24
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)

[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: eba77d7
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: e933ac6
• Duration 1:38:21
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: eba77d7
• Duration 1:10:41
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: eba77d7
• Duration 1:45:49
• Result: ❌ FAILED
• Error: Error while executing command: make -C tests test_ycsb.run. Reason: exit status 2
• Build Logs (available for 30 days)