Zgoda91

[xDS] A97 - JWT token file call creds

6

implementing gRFC A97 [grpc/proposal#492](https://github.com/grpc/proposal/pull/492)

[xDS] A65 mTLS credentials in bootstrap (part 2)

4

implementing gRFC A65 [grpc/proposal/pull/372](https://github.com/grpc/proposal/pull/372) This change contains: 1. Updated `TlsChannelCredentials` instantiation process, which involves reading trust certificates from paths provided in the bootstrap configuration file. 2. Trust certificates polling mechanism...

implementing gRFC A65 [proposal/pull/372](https://github.com/grpc/proposal/pull/372). This change contains: 1. New aggregate `ResourceAllocatingChannelCredentials` class that holds a `ChannelCredentials` instance and associated list of `Closeable` objects representing resources allocated during given `ChannelCredentials` instantiation....