[Python][C++][FlightRPC] Add client option to disable server validation

[asfimport]

Note that this requires using grpc-cpp version 1.25 or higher.

This requires using GRPC's TlsCredentials class, which is in a different namespace for 1.25-1.31 vs. 1.32+ as well.

This class and its related options provide an option to disable server certificate checks and require the caller to supply a callback to be used instead.

Reporter: James Duong / @jduo
Assignee: James Duong / @jduo

PRs and other links:

• GitHub Pull Request #8325

_{Note: This issue was originally created as ARROW-10206. Please see the migration documentation for further details.}

[asfimport]

James Duong / @jduo:
In the PR above, we support building against multiple versions of gRPC.

1. Prior to 1.27, the features in gRPC needed to support this don't exist. The option to disable server verification fails at runtime if used.
2. Between 1.27 to 1.31 (inclusive), the features needed are in the grpc_impl::experimental namespace. Compile the code in Flight client using that namespace.
3. From 1.32 and later, the features are in the grpc::experimental namespace. Compile the code in Flight client using that namespace.

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 8325
#8325