Add python wheel egg relationships (#2903)

* add python package relationships

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* nil for empty relationships collections

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* new json schema for optional python requiremenets

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* update format snapshots for python packages

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* decompose python parsers more + add tests around plural fields

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* update JSON schema with python dep refs

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

syft/format/syftjson/test-fixtures/snapshot/TestDirectoryEncoder.golden

@@ -1,7 +1,7 @@
 {
  "artifacts": [
   {
-   "id": "fb6bef15e281ea43",
+   "id": "5a2b1ae000fcb51e",
    "name": "package-1",
    "version": "1.0.1",
    "type": "python",

syft/format/syftjson/test-fixtures/snapshot/TestEncodeFullJSONDocument.golden

@@ -1,7 +1,7 @@
 {
  "artifacts": [
   {
-   "id": "d748d4614750058d",
+   "id": "ad3ecac55fe1c30f",
    "name": "package-1",
    "version": "1.0.1",
    "type": "python",

syft/format/syftjson/test-fixtures/snapshot/TestImageEncoder.golden

@@ -1,7 +1,7 @@
 {
  "artifacts": [
   {
-   "id": "80210ebcba92e632",
+   "id": "c5cf7ac34cbca450",
    "name": "package-1",
    "version": "1.0.1",
    "type": "python",