Lift concurrent query semaphore limit by default

[hiltontj]

Problem statement

The query executor has a hard-coded limit on the concurrent query semaphore of 10:

influxdb/influxdb3/src/commands/serve.rs

Line 520 in ef3599d

concurrent_query_limit: 10,

This should be higher by default, and also be configurable.

Proposed solution

Completely remove the limit by default by setting the default to the max for tokio's semaphore (see Semaphore::MAX_PERMITS).

Make the value configurable in the CLI arguments with a --max-concurrent-queries argument.

Alternatives

Don't allow a configurable limit, and just set it internally to Semaphore::MAX_PERMITS.

Additional context

The value of 10 likely came from IOx, where the default value for that semaphore in the querier is chosen as 10. There, however, that is being set on a per-querier basis, so they can support more concurrent queries in practice via multiple nodes.

See also: #25615