Support babashka.process reload for exec fn (#1558)

* Support babashka.process reload for exec fn

Exposed GraalVM `ProcessProperties/exec` signature used by
babashka.process/exec.

Add new `graal?` feature (on by default) to allow folks to build/use
babashka without this specific Graal API.

On my linux dev box bb executable increased by 8kb.

Closes #1557

* Respond to PR review feedback

1. Allow all Graal ProcessProperties/exec signatures

2. Instead of a feature flag, simply check if Graal ProcessProperties
class is available before including ProcessProperties/exec.
I did not see the value of adding a has-graal-process-properties fn, so
left that part out. Lemme know if you want/need that.

* Respond to PR review feedback

Because resolves can bloat GraalVM native-image size, we like to keep
the together and obvious instead of buried and non-obvious.

CHANGELOG.md

@@ -14,6 +14,7 @@ in the CfP!
 ## Unreleased
 
 - [#1524](https://github.com/babashka/babashka/issues/1524): Remove dynamic builds for linux-aarch64 ([@lispyclouds](https://github.com/lispyclouds))
+- [#1577](https://github.com/babashka/babashka/issues/1557): Add support for `babashka.process/exec` after namespace reload of `babashka.process` ([@lread](https://github.com/lread)) 
 
 ## 1.3.179 (2023-04-26)
 

src/babashka/impl/classes.clj

@@ -15,6 +15,9 @@
 (def has-domain-sockets?
   (resolve 'java.net.UnixDomainSocketAddress))
 
+(def has-graal-process-properties?
+  (resolve 'org.graalvm.nativeimage.ProcessProperties))
+
 (def base-custom-map
   `{clojure.lang.LineNumberingPushbackReader {:allPublicConstructors true
                                               :allPublicMethods true}
@@ -182,7 +185,11 @@
                             `java.util.ResourceBundle
                             {:methods [{:name "getBundle"
                                         :parameterTypes ["java.lang.String","java.util.Locale",
-                                                         "java.lang.ClassLoader"]}]})))
+                                                         "java.lang.ClassLoader"]}]})
+
+    has-graal-process-properties?
+    (assoc `org.graalvm.nativeimage.ProcessProperties
+           {:methods [{:name "exec"}]})))
 
 (def java-net-http-classes
   "These classes must be initialized at run time since GraalVM 22.1"