gnu: telegram-desktop: Use modern package style.

gnu: telegram-desktop: Use modern package style.

* gnu/packages/telegram.scm (%telegram-version)
(cmake-helpers-for-telegram-desktop, codegen-for-telegram-desktop)
(lib-base-for-telegram-desktop, lib-crl-for-telegram-desktop)
(lib-lottie-for-telegram-desktop, lib-qr-for-telegram-desktop)
(lib-rlottie-for-telegram-desktop,lib-rpl-for-telegram-desktop)
(lib-spellcheck-for-telegram-desktop, lib-storage-for-telegram-desktop)
(lib-tl-for-telegram-desktop, lib-ui-for-telegram-desktop)
(lib-waylandshells-for-telegram-desktop, lib-webrtc-for-telegram-desktop)
(lib-webview-for-telegram-desktop, tgcalls-for-telegram-desktop): New variables.
(telegram-desktop)[arguments]: Convert to list of G-Expressions.
<#:phases>: Inline cmake-helpers-for-telegram-desktop,
codegen-for-telegram-desktop, lib-base-for-telegram-desktop,
lib-crl-for-telegram-desktop, lib-lottie-for-telegram-desktop,
lib-qr-for-telegram-desktop, lib-rlottie-for-telegram-desktop,
lib-rpl-for-telegram-desktop, lib-spellcheck-for-telegram-desktop,
lib-storage-for-telegram-desktop, lib-tl-for-telegram-desktop,
lib-ui-for-telegram-desktop, lib-waylandshells-for-telegram-desktop,
lib-webrtc-for-telegram-desktop, lib-webview-for-telegram-desktop,
and tgcalls-for-telegram-desktop.
[native-inputs]: Remove cmake-helpers.  Drop labels.
[inputs]: Remove codegen-source, lib-base-source, lib-crl-source,
lib-lottie-source, lib-qr-source, lib-rlottie-source, lib-rpl-source,
lib-spellcheck-source, lib-storage-source, lib-tl-source, lib-ui-source,
lib-waylandshells-source, lib-webrtc-source, lib-webview-source and
tgcalls-source.  Drop labels.

Signed-off-by: Liliana Marie Prikler <liliana.prikler@gmail.com>