feat(cbor): add encoding/decoding for new Map() instance

[BlackAsLight]

Closes: #6249

These changes adds support for accepting a Map instance in encodeCbor and returning it again from decodeCbor. It achieves this via the 259 tag number (Spec).

While the code is mostly the same for encoding and decoding Objects, it differs in the need for limiting keys to only strings. It also guarantees that the order isn't at risk of being changed due to encoding/decoding.

This pull request does not add support for accepting Map instances via the streaming methods of this library. The logistics for decoding that is a bit more trickier to figure out.

import { assertEquals } from "@std/assert";
import { type CborType, decodeCbor, encodeCbor } from "@std/cbor";

assertEquals(
  decodeCbor(encodeCbor(new Map([[ 1, 2 ], [ "3", 4 ], [ [5], { a: 6 } ]]))),
  new Map([[ 1, 2 ], [ "3", 4 ], [ [5], { a: 6 } ]])
);

[codecov]

Codecov Report

Attention: Patch coverage is 87.80488% with 10 lines in your changes missing coverage. Please review.

Project coverage is 96.51%. Comparing base (7480f35) to head (5a5a256).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
cbor/_common_decode.ts	88.00%	6 Missing ⚠️
cbor/_common_encode.ts	86.66%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6252      +/-   ##
==========================================
- Coverage   96.52%   96.51%   -0.02%     
==========================================
  Files         535      535              
  Lines       41030    41108      +78     
  Branches     6141     6161      +20     
==========================================
+ Hits        39606    39676      +70     
- Misses       1382     1390       +8     
  Partials       42       42              

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[kt3k]

LGTM