Convert errors thrown from interceptors (#2209)

Motivation:

gRPC checks whether errors thrown from interceptors are `RPCError` and
otherwise treats them as `unknown` (to avoid leaking internal
information). There is a third possibility: the error is explicitly
marked as being convertible to an `RPCError`. This check is currently
missing when thrown from client/server interceptors.

Modifications:

- Catch `RPCErrorConvertible` in the client/server executors when thrown
from interceptors
- Add tests

Result:

Error information isn't dropped

Fix build issues with static Linux SDK (#2206)

This PR fixes some imports so that grpc-swift can be built using the
static Linux SDK.

Rename nightly_6_1 params to nightly_next (#2203)

Rename nightly_6_1 params to nightly_next; see
apple/swift-nio#3122

Update dependency requirements and docs (#2188)

Update dependencies for rc (#2181)

Motivation:

We're going to tag an RC soon so bump tutorial/example dependencies.

Modifications:

- Bump dependencies to `-rc.1`.

Result:

Docs will be correct for the tagged release.

Update tutorials for beta 3 (#2165)

Motivation:

We're going to tag beta 3 soon, so ensure the tutorials are up to date.

Modifications:

- Update tutorials

Result:

More up-to-date docs

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Co-authored-by: Gus Cairo <me@gustavocairo.com>

Bump versions (#2150)

Update generated code (#2141)

Bump version number to 1.24.2 (#2111)

Motivation:

We plan on tagging a release soon.

Modifications:

- Bump the version to 1.24.2

Result:

The version in the default user-agent string will match the released
version.

Bump version number to 1.24.0 (#2088)

Motivation:

We plan on tagging a release soon.

Modifications:

- Bump the version to 1.24.0

Result:

The version in the default user-agent string will match the released
version.