Introduce minimal source coordinates (#623)

* split source.Location and create source.Coordinates for minimal path addressing

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

* move coordinates into separate file

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

* Update syft/source/coordinates.go

Co-authored-by: Dan Luhring <luhring@users.noreply.github.com>

internal/formats/syftjson/test-fixtures/snapshot/TestDirectoryPresenter.golden

@@ -1,7 +1,7 @@
 {
  "artifacts": [
   {
-   "id": "cbf4f3077fc7deee",
+   "id": "2a115ac97d018a0e",
    "name": "package-1",
    "version": "1.0.1",
    "type": "python",
@@ -36,7 +36,7 @@
    }
   },
   {
-   "id": "1a39aadd9705c2b9",
+   "id": "5e920b2bece2c3ae",
    "name": "package-2",
    "version": "2.0.1",
    "type": "deb",

internal/formats/syftjson/test-fixtures/snapshot/TestImagePresenter.golden

@@ -1,7 +1,7 @@
 {
  "artifacts": [
   {
-   "id": "d1d433485a31ed07",
+   "id": "888661d4f0362f02",
    "name": "package-1",
    "version": "1.0.1",
    "type": "python",
@@ -32,7 +32,7 @@
    }
   },
   {
-   "id": "2db629ca48fa6786",
+   "id": "4068ff5e8926b305",
    "name": "package-2",
    "version": "2.0.1",
    "type": "deb",