Azure secp bulk loading

[jframe]

PR Description

Add bulk loading of secp keys to the eth1 mode of Web3Signer.

This adds the following new command line options to web3signer eth1 subcommand:

• --azure-vault-enabled
• --azure-vault-auth-mode
• --azure-vault-name
• --azure-client-id
• --azure-tenant-id
• --azure-client-secret
• --azure-tags

Changes

• Add mapKeyProperties to AzureKeyVault to enable processing of Azure keys
• Created Azure bulk loader to iterate over the keys in the vault and create EthSecpArtifactSigner's
• Remove ForkJoinPool hack and use an ExecutorService as the with problem blocking ForkJoin pool is also an issue with iterating over the Azure keys
• Change usage of Azure code to use the AzureKeyVaultFactory instead of the static constructors of the AzureKeyVault so the ExecutorService can be reused and shutdown correctly
• Add Azure bulk loading paremeters to the Eth1 config

Fixed Issue(s)

fixes #832

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

Testing

• I thought about testing these changes in a realistic/non-local environment.

[siladu]

Good test coverage 👍
Just some nits really.

[siladu]

nit/musing: could potentially simplify by using a ConcurrentHashMap, but with the downside of a redundant key name. Don't think it's worth it, was just an interesting pattern to review...

return executorServiceCache.computeIfAbsent(
        "key",
        e -> Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors()));

[gfukushima]

some nits, otherwise lgtm

[siladu]

The Runners are much more comprehensible now 👍