Attempt to refactor SVGMobject with svgelements (#1731)

* Some small refactors

* Refactor MTex

* Implement TransformMatchingMTex

* Some refactors

* Some refactors

* Some small refactors

* Strip strings before matching

* Implement get_submob_tex

* Use RGB color mode

* Some small refactors

* Try refactoring SVGMobject with svglib

* Refactor SVGMobject using svgelements

* Refactor SVGMobject using svgelements

* Use functions instead of func names as dict values

* style: modify import order to conform to PEP8

* Set default values to None

* modify import order

* Remove unused import

Co-authored-by: TonyCrane <[email protected]>