[Java] Add copy functions to Table

[asfimport]

Add copyVector() and copy() (to copy the whole Table) to the Table interface.

 

The copy vector methods support the use-case where someone really needs a vector (rather than, say, a FieldReader), but we don't want to break immutability. 

 

The copy table method supports the use-case of wanted to make a working copy of a table before converting the original to a VectorSchemaRoot

Reporter: Larry White / @lwhite1
Assignee: Larry White / @lwhite1

PRs and other links:

• GitHub Pull Request #14389

_{Note: This issue was originally created as ARROW-18014. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 14389
#14389