Adds a standalone job for running decrypt private membership queries

[jonmolle]

Adds a standalone decrypt job to the panel exchange tools.

[wfa-reviewable]

This change is 

[stevenwarejones]

A few comments but I'm happy to just land this and I can take care of what I said in a follow-up

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @jonmolle)

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src/main/kotlin/org/wfanet/panelmatch/client/tools/DecryptPrivateMembershipQueryResults.kt line 95 at r1 (raw file):

  @Option(
    names = ["--exchange-step-file"],

an exchange step implies an exchange-date. I'd prefer something slightly more flexible that passes in separate flags for exchangeworkflow and exchange-date and step-index and doesn't require reserialization for each day you want to run. I can do this in a follow up if you prefer since I already have this change on my branch.

Also, a nit but maybe just change the filename to BeamJobsMain.kt -- we can extend it to run any beam step.

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src/main/kotlin/org/wfanet/panelmatch/client/tools/DecryptPrivateMembershipQueryResults.kt line 162 at r1 (raw file):

  private fun makePipelineOptions(): PipelineOptions {
    return PipelineOptionsFactory.`as`(BeamOptions::class.java).apply {

nit: we really shouldn't use BeamOptions here as it extends Dataflow only options, but I can take care of that in a follow-up.

[stevenwarejones]

Lets close this one out.

Reviewable status: 0 of 2 files reviewed, 2 unresolved discussions (waiting on @jonmolle)