Fix integer parsing logic

[dbussink]

We have various places where the types of what we parse and then use don't align. This is something CodeQL correctly warns about that it can lead to unexpected behavior with truncation.

This fixes those cases that CodeQL is complaining about.

Related Issue(s)

https://github.com/vitessio/vitess/security/code-scanning/793
https://github.com/vitessio/vitess/security/code-scanning/792
https://github.com/vitessio/vitess/security/code-scanning/1931
https://github.com/vitessio/vitess/security/code-scanning/1927
https://github.com/vitessio/vitess/security/code-scanning/1926
https://github.com/vitessio/vitess/security/code-scanning/1925
https://github.com/vitessio/vitess/security/code-scanning/1924
https://github.com/vitessio/vitess/security/code-scanning/1923
https://github.com/vitessio/vitess/security/code-scanning/1922
https://github.com/vitessio/vitess/security/code-scanning/1921

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

Review Checklist

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General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

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Backward compatibility

• Protobuf changes should be wire-compatible.
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• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 73.52941% with 9 lines in your changes missing coverage. Please review.

Project coverage is 67.74%. Comparing base (9c6c380) to head (829caf0).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtctl/grpcvtctldserver/server.go	16.66%	5 Missing ⚠️
go/vt/vttablet/tabletmanager/rpc_replication.go	0.00%	2 Missing ⚠️
go/vt/vtcombo/tablet_map.go	0.00%	1 Missing ⚠️
go/vt/vttablet/faketmclient/fake_client.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17650      +/-   ##
==========================================
- Coverage   67.76%   67.74%   -0.03%     
==========================================
  Files        1586     1586              
  Lines      255763   255767       +4     
==========================================
- Hits       173315   173264      -51     
- Misses      82448    82503      +55     

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