Build RPM packages only

Build rpm packages only

Build rpm packages only

Integrate vcpkg to manage dependencies for all platforms (apache#371)

### Motivation

Currently we manage dependencies by ourselves:
- When running unit tests in CI, dependencies are installed from the
  Debian package management tool `apt`
- When verifying macOS build, dependencies are installed from the
  Homebrew package manager
- When verifying Windows build, dependencies are installed via vcpkg but
  no versions are specified
- When building pre-built binaries to release, dependencies are
  installed by scripts under `pkg/` directories. These scripts download
  the source code according to `dependencies.yaml` and build

It makes the pre-built binaries never tested except for the simple
manual tests when voting for a new release. As a result, regression like
apache#363 could happen.

This patch aims at integrating vcpkg to manage dependencies for all
platforms, not only for Windows.

### Modifications

Integrate the CMakeLists.txt with vcpkg by:
1. Introduce vcpkg as a submodule of this project
2. Update `vcpkg.json` to specify dependency versions.
3. Set `CMAKE_TOOLCHAIN_FILE` with the `vcpkg.cmake` in the submodule.

Then, we can simply use `find_package` to find all dependencies and
depend on them via a target like `CURL::libcurl` to have all include
directores and link libraries.

Update the `unit-tests` workflow to verify building the binaries via
vcpkg to test. The README is also updated to show how much simpler to
build with vcpkg now.

### TODO

There are still some tasks that cannot be done by vcpkg:
1. The static library (e.g. `libpulsarwithdeps.a`) that bundles all
   3rd-party dependencies.
2. The pre-built binaries are still built by scripts under `./pkg`
   directory. Specifically, vcpkg does not work with GCC 4.8 so on
   CentOS 7 we still need to build dependencies manually.

So the previous CMakeLists.txt are retained and will be used if
`INTEGRATE_VCPKG` is OFF (by default). They will be removed until the
task above can be done by vcpkg in future.

We also need to update `dependencies.yaml` to be consistent with
`vcpkg.json` if all tasks above cannot be replaced by vcpkg.

(cherry picked from commit 7baa312)

Bumped version to 3.5.0-rc1

Use Rocky Linux to build RPM packages

The RPM packages will be built with GCC 5 ABI to be compatible with new
GCC versions.

Fix Protobuf symbols not found in libpulsarwithdeps.a when building o…

…n macOS (apache#354)

### Motivation

apache#290 brings a regression
that on macOS, Protobuf is always found with CMake Config mode, which
does not set the `Protobuf_LIBRARIES` variable so that the
libpulsarwithdeps.a misses the symbols of Protobuf.

### Modifications

When `LINK_STATIC` is ON, use CMake Module mode to find the Protobuf.

Add `build-static-library.sh` to build libraries with static
dependencies and verify these libraries in PR workflow. Upload the
pre-built binaries in the build workflow.

(cherry picked from commit f75b39b)

Add warning logs for reconnection

(cherry picked from commit 3d84e76)

Add warning logs for reconnection

Add more logs for reconnection