[FEATURE REQ] [Keyvault-JCA] Offer custom properties besides system properties for vault parameters

[Clemthor]

KeyVaultKeyStore currently only supports system properties. If more than one key vault shall be accessed from an application this needs some special handling (setting and removing system properties on the fly). It would be more comfortable to be able to directly pass the correct properties when creating a keystore.

[github-actions]

@adarce @alukovenko-ms @cheathamb36 @Cherrett @chlowell @dhanvikapila @dragav @fponzi-ms @FRL200 @jackrichins @kasturi3k @ksemenov-gh @kurtzeborn @mancycakv @marekkarbarz @melissamserv @ncamillucci @osmuller @rahulalapati43 @seanbamsft @sebansal @vakuncha @vickm

[github-actions]

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