GH-552: [Vector] Add absent methods to the UnionFixedSizeListWriter

[axreldable]

What's Changed

Add absent methods to the UnionFixedSizeListWriter.

1. Aligned the UnionFixedSizeListWriter template with the UnionListWriter template, which added the following previously absent methods to the generated UnionFixedSizeListWriter class:

- duration() methods
    - DurationWriter duration()
    - DurationWriter duration(String name, org.apache.arrow.vector.types.TimeUnit unit)
    - DurationWriter duration(String name)
- timeStampSecTZ() methods
    - TimeStampSecTZWriter timeStampSecTZ()
    - TimeStampSecTZWriter timeStampSecTZ(String name, String timezone)
    - TimeStampSecTZWriter timeStampSecTZ(String name)
- timeStampMilliTZ() methods
    - TimeStampMilliTZWriter timeStampMilliTZ()
    - TimeStampMilliTZWriter timeStampMilliTZ(String name, String timezone)
    - TimeStampMilliTZWriter timeStampMilliTZ(String name)
- timeStampMicroTZ() methods
    - TimeStampMicroTZWriter timeStampMicroTZ()
    - TimeStampMicroTZWriter timeStampMicroTZ(String name, String timezone)
    - TimeStampMicroTZWriter timeStampMicroTZ(String name)
- timeStampNanoTZ() methods
    - TimeStampNanoTZWriter timeStampNanoTZ()
    - TimeStampNanoTZWriter timeStampNanoTZ(String name, String timezone)
    - TimeStampNanoTZWriter timeStampNanoTZ(String name)
- fixedSizeBinary() methods
    - FixedSizeBinaryWriter fixedSizeBinary()
    - FixedSizeBinaryWriter fixedSizeBinary(String name, int byteWidth)
    - FixedSizeBinaryWriter fixedSizeBinary(String name)
- write() methods for Duration
    - void writeDuration(long value)
    - void write(DurationHolder holder)
- write() methods for TimeStampSecTZ 
    - void writeTimeStampSecTZ(long value)
    - void write(TimeStampSecTZHolder holder)
- write() methods for TimeStampMilliTZ
    - void writeTimeStampMilliTZ(long value)
    - void write(TimeStampMilliTZHolder holder)
- write() methods for TimeStampMicroTZ
    - void writeTimeStampMicroTZ(long value)
    - void write(TimeStampMicroTZHolder holder)
- write() methods for TimeStampNanoTZ
    - void writeTimeStampNanoTZ(long value)
    - void write(TimeStampNanoTZHolder holder)
- write() methods for FixedSizeBinary
    - void writeFixedSizeBinary(ArrowBuf buffer)
    - void write(FixedSizeBinaryHolder holder)

2. Add structName = name; for 2 existing methods (align them with other similar methods):

- DecimalWriter decimal(String name)
- Decimal256Writer decimal256(String name)

3. Remove unused assignments from the UnionListWriter template.

This fix doesn't change the code of the UnionListWriter generated class and extend/fix the code of the UnionFixedSizeListWriter generated class. So, the change is backward compatible.

See this gist for a diff of the generated UnionFixedSizeListWriter class.

---

Inspired by this PR.

---

Closes #552 .

[github-actions]

Thank you for opening a pull request!

Please label the PR with one or more of:

• bug-fix
• chore
• dependencies
• documentation
• enhancement

Also, add the 'breaking-change' label if appropriate.

See CONTRIBUTING.md for details.

[axreldable]

Please add the enhancement label.