Clean up use of references in Spicy SSL analyzer

The Spicy SSL analyzer was using references pretty heavily, probably to
work around now fixed issues with `inout` parameters in older Spicy
versions. At least for units this seems not needed anymore, and was also
partially incorrect, e.g., the Spicy docs call out that when using
`inout` parameters, passed and expected types should match exactly so
passing a reference as an `inout` value seems incorrect. Additionally,
one use case for references in Spicy is to use their interior
mutability, i.e., a reference never needs to be passed `inout` since
their can always be mutated.

Internally units are stored as reference-counted values, and references
to units are not much cheaper since they also need to be refcounted.
With that there seems litle reason to use references in this analyzer at
all, and this patch drops their use completely; instead we either pass
values, or values declared `inout`.

We leave the use of references for sharing sinks in place.

src/analyzer/protocol/ssl/spicy/SSL.spicy

@@ -862,16 +862,16 @@ type Heartbeat = unit(sh: Share, length: uint16) {
 };
 
 # note - this will mostly be garbage because it is encrypted.
-public type Alert = unit(sh: Share&) {
+public type Alert = unit(sh: Share) {
     alerts: Alert_message(sh)[];
 };
 
-type Alert_message = unit(sh: Share&) {
+type Alert_message = unit(sh: Share) {
     level: uint8; # &convert=AlertLevel($$);
     description: uint8; # &convert=AlertDescription($$);
 };
 
-type Handshake = unit(inout msg: Message, sh: Share&) {
+type Handshake = unit(inout msg: Message, inout sh: Share) {
     handshakes: Handshake_message(msg, sh)[];
 };
 
@@ -1904,7 +1904,7 @@ public function convert_certificate_authorities(c: vector<CertificateAuthority>)
 }
 
 # returns true for the "client"
-public function get_direction(sh: Share&): bool {
+public function get_direction(sh: Share): bool {
     if (sh.flipped)
         return !zeek::is_orig();
     else