Add permission to write logs to Stackdriver by default

[alaladeakin]

How to categorize this PR?

/area logging
/kind enhancement
/platform gcp

What this PR does / why we need it:
This PR adds Stackdriver permissions to Gardener nodes. With this (default) permission, operators do not need to do anything additional after deploying fluentbit or other logging mechanisms.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Release note:

[gardener-robot]

@alaladeakin Labels area/todo, kind/todo do not exist.

[CLAassistant]

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[gardener-robot]

@alaladeakin Thank you for your contribution.

[gardener-robot-ci-3]

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[gardener-robot]

@alaladeakin Labels area/todo, kind/todo do not exist.