Move test modules from contrib to src/test/modules

This is advance preparation for introducing even more test modules; the
easy solution is to add them to contrib, but that's bloated enough that
it seems a good time to think of something different.

Moved modules are dummy_seclabel, test_shm_mq, test_parser and
worker_spi.

(test_decoding was also a candidate, but there was too much opposition
to moving that one.  We can always reconsider later.)

src/test/modules/test_parser/test_parser--1.0.sql

@@ -0,0 +1,32 @@
+/* src/test/modules/test_parser/test_parser--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION test_parser" to load this file. \quit
+
+CREATE FUNCTION testprs_start(internal, int4)
+RETURNS internal
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION testprs_getlexeme(internal, internal, internal)
+RETURNS internal
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION testprs_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION testprs_lextype(internal)
+RETURNS internal
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE TEXT SEARCH PARSER testparser (
+    START    = testprs_start,
+    GETTOKEN = testprs_getlexeme,
+    END      = testprs_end,
+    HEADLINE = pg_catalog.prsd_headline,
+    LEXTYPES = testprs_lextype
+);