Make procedure mismatch more informative with pragma/call convention mismatches

[beef331]

The following is a few showcases of the output changes

Examples:

proc a(a: int, c: float){.cdecl.} = echo "Hmm"
var b: proc(a: int, c: float){.noSideEffect.} = a
b(10, 3.14)

Used to output:

Error: type mismatch: got 'proc (a: int, c: float){.cdecl, gcsafe, locks: 0.}' for 'a' but expected 'proc (a: int, c: float){.closure, noSideEffect.}'

Now outputs:

Error: type mismatch: got 'proc (a: int, c: float){.cdecl, gcsafe, locks: 0.}' for 'a' but expected 'proc (a: int, c: float){.closure, noSideEffect.}'
Pragma mismatch got '{..}', but expected '{.noSideEffect.}'.

proc a(a: int, c: float){.cdecl.} = echo "Hmm"
var b: proc(a: int, c: float){.nimcall, noSideEffect.} = a
b(10, 3.14)

Used to output:

Error: type mismatch: got 'proc (a: int, c: float){.cdecl, gcsafe, locks: 0.}' for 'a' but expected 'proc (a: int, c: float){.nimcall, noSideEffect.}'

Now Outputs:

Error: type mismatch: got 'proc (a: int, c: float){.cdecl, gcsafe, locks: 0.}' for 'a' but expected 'proc (a: int, c: float){.nimcall, noSideEffect.}'
Calling convention mismatch got '{.cdecl.}' but expected '{.nimcall.}'.
Pragma mismatch got '{..}', but expected '{.noSideEffect.}'.

[ringabout]

Please add a test.

[beef331]

Tests will be added, Timothee wanted the PR up so there could be some discussion to what this should contain, so after there is a agreement on what this should show/do and I implement it we'll get tests.

[timotheecour]

LGTM, the remaining comments are not critical and can be addressed in followup PR; great addition!

[timotheecour]

CI failure unrelated => SciNim/Datamancer#10