Introduce new format pattern + port json processing (#550)

* add new format pattern

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

* add syftjson format

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

* add internal formats helper

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

* add SBOM encode/decode to lib API

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

* remove json presenter + update presenter tests to use common utils

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

* remove presenter format enum type + add formats shim in presenter helper

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

* add MustCPE helper for tests

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

* update usage of format enum

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

* add test fixtures for encode/decode tests

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

* fix integration test

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

* migrate format detection to use reader

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

* address review comments

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

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

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+this file has contents

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

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+file-2 contents!