gcrypt: Remove limited crypto plugin

This has not seen any significant changes for years.  So it lacks support
for modern algorithms and would require quite some work for an overhaul.
Given that we support several other crypto backends, let's just remove
this to reduce the maintenance burden.

The test scenarios and other references are also removed.

scripts/dh_speed.sh

@@ -11,15 +11,12 @@ function modptest {
 }
 
 echo "testing gmp"
-# gmp needs an RNG plugin, pick gcrypt
-modptest "gmp gcrypt"
+# gmp needs an RNG plugin, pick random
+modptest "gmp random"
 
 echo "testing curve25519"
-# curve25519 needs an RNG plugin, pick gcrypt
-$DIR/dh_speed "curve25519 gcrypt" 300 curve25519 curve25519 | tail -n 1
-
-echo "testing gcrypt"
-modptest "gcrypt"
+# curve25519 needs an RNG plugin, pick random
+$DIR/dh_speed "curve25519 random" 300 curve25519 curve25519 | tail -n 1
 
 echo "testing openssl"
 modptest "openssl"

scripts/pubkey_speed.sh

@@ -32,8 +32,7 @@ function ecdsatestall {
   ecdsatest secp521r1 "$1" 500
 }
 
-rsatestall "gmp gcrypt pem pkcs1"
-rsatestall "gcrypt pem pkcs1"
+rsatestall "gmp random pem pkcs1"
 rsatestall "openssl pem"
 rsatestall "botan pem"
 ecdsatestall "openssl pem"

scripts/test.sh

@@ -225,11 +225,6 @@ openssl*)
 		TESTS_PLUGINS="$TESTS_PLUGINS kdf"
 	fi
 	;;
-gcrypt)
-	CONFIG="--disable-defaults --enable-pki --enable-gcrypt --enable-random --enable-pem --enable-pkcs1 --enable-pkcs8 --enable-gcm --enable-hmac --enable-kdf --enable-curve25519 --enable-x509 --enable-constraints"
-	export TESTS_PLUGINS="test-vectors gcrypt! random pem pkcs1 pkcs8 gcm hmac kdf curve25519 x509 constraints"
-	DEPS="libgcrypt20-dev"
-	;;
 botan)
 	CONFIG="--disable-defaults --enable-pki --enable-botan --enable-pem --enable-hmac --enable-x509 --enable-constraints --enable-drbg"
 	export TESTS_PLUGINS="test-vectors botan! pem hmac x509 constraints drbg"
@@ -280,7 +275,7 @@ all|alpine|codeql|coverage|sonarcloud|no-dbg|no-testable-ke)
 	DEPS="$DEPS libcurl4-gnutls-dev libsoup-3.0-dev libunbound-dev libldns-dev
 		  libmysqlclient-dev libsqlite3-dev
 		  libldap2-dev libpcsclite-dev libpam0g-dev binutils-dev libnm-dev
-		  libgcrypt20-dev libjson-c-dev libtspi-dev libsystemd-dev
+		  libjson-c-dev libtspi-dev libsystemd-dev
 		  libselinux1-dev libiptc-dev ruby-rubygems python3-build tox"
 	if [ "$ID" = "ubuntu" -a "$VERSION_ID" = "22.04" -a "$1" = "build-deps" ]; then
 		# python3-build is broken on 22.04 with venv (https://bugs.launchpad.net/ubuntu/+source/python-build/+bug/1992108)
@@ -292,7 +287,7 @@ all|alpine|codeql|coverage|sonarcloud|no-dbg|no-testable-ke)
 		# override the whole list for alpine
 		DEPS="git gmp-dev openldap-dev curl-dev ldns-dev unbound-dev libsoup3-dev
 			  libxml2-dev tpm2-tss-dev tpm2-tss-sys mariadb-dev wolfssl-dev
-			  libgcrypt-dev botan3-dev pcsc-lite-dev networkmanager-dev
+			  botan3-dev pcsc-lite-dev networkmanager-dev
 			  linux-pam-dev iptables-dev libselinux-dev binutils-dev libunwind-dev
 			  ruby py3-setuptools py3-build py3-tox"
 		# musl does not provide backtrace(), so use libunwind