Fix inconsistent parameter naming in core Truth subjects.

This change standardizes parameter names across various Subject classes in the `core/src/main/java/com/google/common/truth` directory.

Key changes include:
- Renaming `other` to `expected` in methods like `isNotEqualTo`, `isNotSameInstanceAs`, and in comparison methods within `ComparableSubject`, `DoubleSubject`, `FloatSubject`, and `LongSubject`.
- Standardizing sequence/string/prefix/suffix parameters in `StringSubject`.
- Ensuring `expected` or `element` is used consistently in `IterableSubject` and its `UsingCorrespondence` class.
- Aligning `value` to `expectedValue` in `MapSubject.UsingCorrespondence.doesNotContainEntry` and `MultimapSubject.UsingCorrespondence.doesNotContainEntry`.