Map allocation optimization for client-go/tools/cache

[Adirio]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Pre-allocates 3 maps in different Replace methods that are being created from a slice, so the size is known beforehand.

Which issue(s) this PR fixes:
NONE

Special notes for your reviewer:
The optimization may be really small but it is good practice to pre-allocate in such cases.

Does this PR introduce a user-facing change?:

NONE

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[Adirio]

I requested the CLA to sign it but I did not receive the email. I asked for a resend but figured I would PR this trivial changes already so that it can be reviewed.

[Adirio]

Edited the title, signed the CLA, squashed the 3 commits into 1 and signed it. Should be ready to merge now.

[liggitt]

/ok-to-test
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Adirio, liggitt

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• staging/src/k8s.io/client-go/tools/cache/OWNERS [liggitt]

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[Adirio]

Everything seems to be fine (expected on a trivial PR). What is the next step?

[liggitt]

it's in the merge queue. the bots will take it from here. thanks!