Create termux-shared library package for all termux constants and shared utils

The termux plugins should use this library instead of hardcoding "com.termux" values in their source code.

The library can be included as a dependency by plugins and third party apps by including the following line in the build.gradle where x.xxx is the version number, once its published.

`implementation 'com.termux:termux-shared:x.xxx'`

The `TermuxConstants` class has been updated to `v0.17.0`, `TermuxPreferenceConstants` to `v0.9.0` and `TermuxPropertyConstants` to `v0.6.0`. Check their Changelog sections for info on changes.

Some typos and redundant code has also been fixed.

terminal-view/src/main/java/com/termux/view/TerminalView.java

@@ -249,7 +249,7 @@ public final class TerminalView extends View {
 
     @Override
     public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
-        if (mClient.shouldEnforeCharBasedInput()) {
+        if (mClient.shouldEnforceCharBasedInput()) {
             // Some keyboards seems do not reset the internal state on TYPE_NULL.
             // Affects mostly Samsung stock keyboards.
             // https://github.com/termux/termux-app/issues/686

terminal-view/src/main/java/com/termux/view/TerminalViewClient.java

@@ -30,7 +30,7 @@ public interface TerminalViewClient {
 
     boolean shouldBackButtonBeMappedToEscape();
 
-    boolean shouldEnforeCharBasedInput();
+    boolean shouldEnforceCharBasedInput();
 
     boolean shouldUseCtrlSpaceWorkaround();