port text presenter to a format object (#604)

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

internal/formats/text/test-fixtures/image-simple/Dockerfile

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+# Note: changes to this file will result in updating several test values. Consider making a new image fixture instead of editing this one.
+FROM scratch
+ADD file-1.txt /somefile-1.txt
+ADD file-2.txt /somefile-2.txt

internal/formats/text/test-fixtures/image-simple/file-1.txt

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+this file has contents

internal/formats/text/test-fixtures/image-simple/file-2.txt

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+file-2 contents!

internal/formats/text/test-fixtures/snapshot/TestTextDirectoryPresenter.golden

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+[Path: /some/path]
+[package-1]
+ Version:	 1.0.1
+ Type:		 python
+ Found by:	 the-cataloger-1
+
+[package-2]
+ Version:	 2.0.1
+ Type:		 deb
+ Found by:	 the-cataloger-2
+

internal/formats/text/test-fixtures/snapshot/TestTextImagePresenter.golden

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+[Image]
+ Layer:		 0
+ Digest:	 sha256:fb6beecb75b39f4bb813dbf177e501edd5ddb3e69bb45cedeb78c676ee1b7a59
+ Size:		 22
+ MediaType:	 application/vnd.docker.image.rootfs.diff.tar.gzip
+
+ Layer:		 1
+ Digest:	 sha256:319b588ce64253a87b533c8ed01cf0025e0eac98e7b516e12532957e1244fdec
+ Size:		 16
+ MediaType:	 application/vnd.docker.image.rootfs.diff.tar.gzip
+
+[package-1]
+ Version:	 1.0.1
+ Type:		 python
+ Found by:	 the-cataloger-1
+
+[package-2]
+ Version:	 2.0.1
+ Type:		 deb
+ Found by:	 the-cataloger-2
+