feat: add the option not to include the extra newline of the Tree's __rich_console__

[0zitro]

Type of changes

• Bug fix
• New feature
• Documentation / docstrings
• Tests
• Other

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review.

Description

Provides a simple way to remove the ugly newline after the Tree string representation (for example, when using the rich.Console.capture() for a __repr__ of some tree-like class).

This is done by creating a new parameter end_new_line (name is subject to change) in the Tree constructor. This option will then determine whether the newline will be yold in the __rich_console__. This removes the need to manually delete the newline in the console output afterwards.

Usage examples:

New behaviour:

from rich.tree import Tree
from rich.console import Console

console = Console()

tree = Tree("some tree", end_new_line=False)
with console.capture() as capture:
    console.print(tree)
cap_text = capture.get()

assert cap_text == "some tree" 

Old behaviour (default):

from rich.tree import Tree
from rich.console import Console

console = Console()

tree = Tree("some tree", end_new_line=True) # default value for the `end_new_line`
with console.capture() as capture:
    console.print(tree)
cap_text = capture.get()

assert cap_text == "some tree\n" # maybe "some tree\r\n" on Windows