[jdk21u-dev] RFR: 8313367: SunMSCAPI cannot read Local Computer certs w/o Windows elevation

[Satyen Subramaniam]

Backporting JDK-8313367: SunMSCAPI cannot read Local Computer certs w/o Windows elevation. With the current code, the enhancement developed to allow keystore access provider SunMSCAPI to access the Windows Local Computer keystore, [JDK-6782021](https://bugs.openjdk.org/browse/JDK-6782021), works as expected only if processes are run as elevated. When run with non-elevated access, the SunMSCAPI provider fails to access a read only private key from the Local Computer certificate store. Adjusts code so if the process does not have write permissions, the store is opened as read-only (instead of failing). Ran GHA Sanity Checks, local Tier 1 and 2, and modified test directly. Patch is clean.

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Commit messages:
 - Backport db535c86bc56b89b7213b3b097d80935fe9e8516

Changes: https://git.openjdk.org/jdk21u-dev/pull/1860/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1860&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313367
  Stats: 33 lines in 2 files changed: 5 ins; 22 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1860.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1860/head:pull/1860

PR: https://git.openjdk.org/jdk21u-dev/pull/1860