chore: License fixes

The license.txt file has been replaced with LICENSE for quite a while
now. INAL but it didn't seem accurate to say "hey, checkout license.txt
although there's no such file". Apart from this, there were
inconsistencies in the headers altogether...this change brings
consistency.

These modules were imported from the ERPNext codebase into Frappe.
License header was overlooked at that point. These were contributed
initially by Frappe Technologies Pvt Ltd under GPLv3 (ERPNext's license) and now
we, as Frappe Technologies Pvt Ltd converting them to MIT to comply with
Frappe's license.

 Conflicts:

	frappe/__init__.py

# Conflicts:
#	frappe/__init__.py

chore: Dead dependencies and code cleanup

* Remove six for PY2 compatability since our dependencies are not, PY2
  is legacy.
* Removed usages of utils from future/past libraries since they are
  deprecated. This includes 'from __future__ ...' and 'from past...'
  statements.
* Removed compatibility imports for PY2, switched from six imports to
  standard library imports.
* Removed utils code blocks that handle operations depending on PY2/3
  versions.
* Removed 'from __future__ ...' lines from templates/code generators
* Used PY3 syntaxes in place of PY2 compatible blocks. eg: metaclass

Helpers to get asset path
Python: frappe.utils.jinja_globals.bundled_asset
JS: frappe.assets.bundled_asset

Since it is no longer used

(cherry picked from commit f78b990486)

Since it is no longer used

(cherry picked from commit f78b990486)

Since it is no longer used

Co-authored-by: Suraj Shetty <13928957+surajshetty3416@users.noreply.github.com>

Updating my forked repository with the latest one.