feat: add random string function for upcoming secret generator refact

[adohe]

What type of PR is this?

/kind feature

What this PR does / why we need it:

add random string function for upcoming secret generator refact

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., design docs, usage docs, etc.:

[coveralls]

Pull Request Test Coverage Report for Build 6891886310

• 17 of 17 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.08%) to 75.549%

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Totals
Change from base Build 6891595177:	0.08%
Covered Lines:	6952
Relevant Lines:	9202

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💛 - Coveralls

[liu-hm19]

Where will this method be used? If a randomly generated string based on the current time is added to the rendering logic of application resources, it may potentially cause changes in the generated Spec or Intent with every build/preview/apply operation, which might have an impact on the 3-way diff process.

[ffforest]

Is this only used for non-terraform resources? To generate secrets in terraform resources we should just use the random provider - provides same functionality and handles diff already.

[adohe]

Is this only used for non-terraform resources? To generate secrets in terraform resources we should just use the random provider - provides same functionality and handles diff already.

This is only used for secret generator, so we put this package under secret.

[adohe]

Where will this method be used? If a randomly generated string based on the current time is added to the rendering logic of application resources, it may potentially cause changes in the generated Spec or Intent with every build/preview/apply operation, which might have an impact on the 3-way diff process.

This method will be used to generate random token string if and only if developers don't provide one in configuration also the impact on diff logic is as expected.

[elliotxx]

lgtm