nimble, patches, cli: vendor parseopt3 dependency (#780)

Rationale:

- Although there are benefits to maintaining a patch rather than an
  in-repo forked dependency, the patching process added complexity and
  fragility. And it seems like it might have to become more complex and
  fragile when we start using `nimble lock` with Nim 2.0.

- Help to unblock the Nim 2.0 version bump, which caused the patching
  process to fail in CI on Windows only.

- It's OK if we have to vendor possible future forked code (e.g. of
  jsony or commonmark), rather than maintaining patches.

- A reader of our nimble file can no longer think that configlet fully
  uses cligen.

We do have an integration test in tests/test_binary to assert that
configlet has the desired CLI option parsing behavior.

configlet.nimble

@@ -1,5 +1,3 @@
-import patches/patch
-
 proc getVersionStart: string =
   # Returns the `major.minor.patch` version in the `configlet.version` file
   # (that is, omitting any pre-release version information).
@@ -19,13 +17,9 @@ bin           = @["configlet"]
 
 # Dependencies
 requires "nim >= 1.6.12"
-requires "cligen#8d4e5fb58917eb681d3babd8561ddd175f01df3d"      # 1.6.13 (2023-07-29)
 requires "jsony#ea811bec7fa50f5abd3088ba94cda74285e93f18"       # 1.1.5  (2023-02-09)
 requires "parsetoml#6e5e16179fa2db60f2f37d8b1af4128aaa9c8aaf"   # 0.7.1  (2023-08-06)
 requires "supersnappy#e4df8cb5468dd96fc5a4764028e20c8a3942f16a" # 2.1.3  (2022-06-12)
 
 task test, "Runs the test suite":
   exec "nim r ./tests/all_tests.nim"
-
-before build:
-  ensureThatNimblePackagesArePatched()

src/cli.nim

@@ -1,5 +1,6 @@
 import std/[os, parseutils, strformat, strutils, terminal]
-import pkg/[cligen/parseopt3, supersnappy]
+import pkg/supersnappy
+import patched_libs/parseopt3
 
 type
   ActionKind* = enum
@@ -365,7 +366,7 @@ func formatOpt(kind: CmdLineKind, key: string, val = ""): string =
   ## Returns a string that describes an option, given its `kind`, `key` and
   ## optionally `val`. This is useful for displaying in error messages.
   runnableExamples:
-    import pkg/cligen/parseopt3
+    import patched_libs/parseopt3
     assert formatOpt(cmdShortOption, "h") == "'-h'"
     assert formatOpt(cmdLongOption, "help") == "'--help'"
     assert formatOpt(cmdShortOption, "v", "quiet") == "'-v': 'quiet'"