assert: add partialDeepEqual to strict mode

[semimikoh]

The partialDeepStrictEqual method was not re-exported as partialDeepEqual in strict assertion mode, unlike other methods such as deepEqual and equal.

Add the alias so that strict mode users can call
assert.partialDeepEqual() consistently with the existing naming convention.

Fixes: #62327

When using node:assert/strict, methods like deepEqual and equal
are automatically aliased to their strict counterparts. However,
partialDeepStrictEqual was missing this alias.

This PR adds the partialDeepEqual alias in two places:

1. Assert constructor: when options.strict is true,
   this.partialDeepEqual = this.partialDeepStrictEqual
2. assert.strict object: partialDeepEqual mapped to
   assert.partialDeepStrictEqual

Tests added in test-assert-class.js and test-assert.js
following the existing alias verification pattern.

Fixes: #62327

[Renegade334]

This doesn't really make sense, because there's no non-strict partialDeepEqual method in the assert module.

The aliases are there such that

const { equal } = require("assert"); // loose equal

is analogous to

const { equal } = require("assert/strict"); // strict equal

but there is no analogous method here.

const { partialDeepEqual } = require("assert"); // undefined

[semimikoh]

@Renegade334

That makes sense — I hadn't considered that the aliases exist to map existing non-strict methods to their strict counterparts, not just to remove the "Strict" suffix.

Since there's no partialDeepEqual in the base assert module, adding the alias in strict mode would be inconsistent.

I'll close #62332.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.68%. Comparing base (d729bec) to head (f72eef0).
⚠️ Report is 763 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62332      +/-   ##
==========================================
+ Coverage   88.55%   89.68%   +1.13%     
==========================================
  Files         703      676      -27     
  Lines      208259   206581    -1678     
  Branches    40162    39558     -604     
==========================================
+ Hits       184415   185277     +862     
+ Misses      15844    13447    -2397     
+ Partials     8000     7857     -143     

Files with missing lines	Coverage Δ
lib/assert.js	98.23% <100.00%> (+<0.01%)	⬆️

... and 355 files with indirect coverage changes

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