[refactor]: introduce syn 2.0, manyhow and darling for proc-macros

[DCNick3]

Description

This PR adds syn 2.0 to the workspace (under the name of syn2, to allow co-existence of different versions).

It then updates iroha_version_derive, iroha_primitives_derive and iroha_derive to use syn2, as well as moving from unmaintained proc-macro-error to manyhow.

It also changes some macro APIs:

I also propose the following changes for VariantCount macro (not yet implemented):

• confusingly, attributes for VariantCount are placed on fields instead of enum variants. I suggest we move them to variants, as it's really a property of the variant
• the naming of #[skip_try_from] is confusing in the context of #[skip_from]: the different in names is in the try, but they correspond to different directions of the generated conversions: from is for Variant -> Enum and try_from is for Enum -> Variant. I suggest changing the name to #[skip_into] or #[skip_try_into] to properly represent the change of conversion direction, even if the actual generated trait is From
• Maybe change #[skip_container] to #[skip_from_container]?

Benefits

Unlike proc-macro-error, manyhow is actively maintained and has cleaner API that does not rely on global state.

Using darling streamlines parsing of (most) attributes by using a declarative serde-like model, also providing reasonable error messages.

[coveralls]

Pull Request Test Coverage Report for Build 5689584713

• 183 of 205 (89.27%) changed or added relevant lines in 4 files are covered.
• 4094 unchanged lines in 80 files lost coverage.
• Overall coverage decreased (-1.5%) to 57.945%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
primitives/derive/src/socket_addr.rs	24	25	96.0%
version/derive/src/lib.rs	38	48	79.17%
macro/derive/src/lib.rs	118	129	91.47%

Files with Coverage Reduction	New Missed Lines	%
client_cli/src/main.rs	1	0%
cli/src/main.rs	1	0%
cli/src/torii/pagination.rs	1	98.9%
config/base/src/runtime_upgrades.rs	1	51.72%
config/src/torii.rs	1	96.67%
core/src/smartcontracts/isi/block.rs	1	87.5%
core/src/sumeragi/network_topology.rs	1	96.76%
crypto/src/merkle.rs	1	96.23%
data_model/src/account.rs	1	52.21%
data_model/src/domain.rs	1	47.37%

Totals
Change from base Build 5423219773:	-1.5%
Covered Lines:	19791
Relevant Lines:	34155

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💛 - Coveralls

[Erigara]

Good job!