Switch to Guice#createInjector and add concurrent SQL/PPL regression ITs

[penghuo]

Description

• replace ModulesBuilder#createInjector() with Guice.createInjector(...) in SQLPlugin and TransportPPLQueryAction so the SQLService and PPLService created are not singleton.
• add SQLConcurrencyIT and PPLConcurrencyIT that hammer COUNT/SUM against the shared Index.ACCOUNT data using fixed thread pools.

Related Issues

#4454

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• New PPL command checklist all confirmed.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff or -s.
• Public documentation issue/PR created.

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