[gcloud-sqlproxy] fix #145 use sha1sum instead of randAlphaNum

[danyworks]

What this PR does / why we need it:
for persistance of random suffix, used by instanceShortName. the function randAlphaNum was previously used, is now replaced with a trimmed sha1sum, that is 9 characters long.

This sha1sum is generated using instance name so it remains consistent across multiple calls, as long as the instance name does not change.

Which issue this PR fixes:
fixes #145

Special notes for your reviewer:
I did bumped the chart version, but i guess the bug is in 0.25.3 so it is better to overwrite the version
instead of bumping it.
I bumped it also, so the linter does not create issues.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• Chart Version bumped, is mandatory for any chart changes
• Variables and other changes are documented in the README.md
• Title of the PR starts with chart name (e.g. [gcloud-sqlproxy])

[rimusz]

@danyworks please resolve merge conflicts, thanks

[rimusz]

@danyworks please resolve chart lint issues, thanks