Update syn requirement from 1.0.107 to 2.0.48 (#881)

* Update syn requirement from 1.0.107 to 2.0.48

Updates the requirements on [syn](https://github.com/dtolnay/syn) to permit the latest version.
- [Release notes](https://github.com/dtolnay/syn/releases)
- [Commits](https://github.com/dtolnay/syn/compare/1.0.107...2.0.48)

---
updated-dependencies:
- dependency-name: syn
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

* rtic-macros: attr.path -> attr.path()

* rtic-macros: tokens -> parse_args()

Fix parsing of InitArgs, IdleArgs, *Args

Including HardwareTaskArgs, SoftwareTaskArgs

* rtic-macros: Rename content to input

As syn2 removes the surrounding parenthesis as
part of parse_args() the distinction between
input and content is redundant

* rtic-macros: Handle removal of Expr::Type

Manually parse local_resources

With type ascription de-RFCd syn2 dropped
Expr::Type

* rtic-macros: Syn upgrade CHANGELOG

* rtic-macro: Retain most old errors as they were

Spans are not equal, but good enough

* rtic-macros: syn2 changed some error messages

Additionally some spans were not retained
with the manual parsing workaround

* rtic-macros: clippy fixes

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Henrik Tjäder <henrik@tjaders.com>

rtic-macros/Cargo.toml

@@ -46,7 +46,7 @@ indexmap = "2.0.0"
 proc-macro2 = "1.0.49"
 proc-macro-error = "1.0.4"
 quote = "1.0.23"
-syn = { version = "1.0.107", features = ["extra-traits", "full"] }
+syn = { version = "2.0.48", features = ["extra-traits", "full"] }
 
 [dev-dependencies]
 trybuild = "1.0.73"