macros: Clean up Context use and ensure we don't miss errors #1744

Job	Run time
nightly	3m 17s
docs	3m 34s
msrv	1m 46s
clippy	1m 51s
rustfmt	15s
basics	1s
wasm	1m 16s
test_miri (rune, runtime:: hir::arena:: --skip runtime::vm:: --skip runtime::vm_execution:: )	2m 34s
test_miri (rune-alloc)	6m 5s
no_std (ubuntu-latest, minimal)	1m 10s
test_doc	6m 0s
no_std (macos-latest, minimal)	1m 46s
build_feature (alloc)	3m 23s
test_lib	3m 41s
build_feature (cli)	4m 1s
test_rune	2m 27s
build_feature (cli,doc)	3m 56s
build_feature (cli,fmt)	4m 7s
build_feature (doc)	3m 38s
build_feature (workspace)	3m 32s
build_feature (languageserver)	3m 40s
build_feature (byte-code)	3m 21s
build_feature (capture-io)	3m 17s
build_feature (emit)	3m 19s
	1h 11m 57s

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