Changes

ticdc: Refactor pipeline to download TiCDC binaries to 'bin' directory for improved test execution. (#3848)

This PR updates the `pull_cdc_storage_integration_heavy_next_gen`
pipeline to improve the handling and verification of TiCDC's
dependencies.

The primary motivation for these changes is to ensure that the necessary
TiDB components (TiDB, TiKV, PD, TiFlash) are correctly downloaded and
accessible before the integration tests are run. This will help prevent
test failures that are caused by missing or incorrectly configured
dependencies.

Changes include:

* The directory for downloading third-party binaries has been renamed
from `third_party_download` to `bin` for clarity and consistency.
* Added a step to explicitly check for the presence and version of
`tidb-server`, `pd-server`, `tikv-server`, and `tiflash` within the
`bin` directory. This provides better visibility into the downloaded
dependencies.
* The `make check_third_party_binary` command is now executed to ensure
all required binaries are present and executable.
* The actual integration test execution command remains, ensuring that
the tests still run as intended after the dependency checks.

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Signed-off-by: tenfyzhong <tenfy@tenfy.cn>
 (commit: 6c293b0)