Make TimeZone no longer allocate over FFI (#572)

This also moves a lot of internal stuff to taking TimeZone instead of
&TimeZone. I think that's fine but I can revert if requested.

Author: Manishearth

src/builtins/compiled/instant.rs

@@ -11,7 +11,7 @@ impl Instant {
     /// Enable with the `compiled_data` feature flag.
     pub fn to_ixdtf_string(
         &self,
-        timezone: Option<&TimeZone>,
+        timezone: Option<TimeZone>,
         options: ToStringRoundingOptions,
     ) -> TemporalResult<String> {
         self.to_ixdtf_string_with_provider(timezone, options, &*TZ_PROVIDER)
@@ -23,7 +23,7 @@ impl Instant {
     /// Enable with the `compiled_data` feature flag.
     pub fn to_ixdtf_writeable(
         &self,
-        timezone: Option<&TimeZone>,
+        timezone: Option<TimeZone>,
         options: ToStringRoundingOptions,
     ) -> TemporalResult<impl writeable::Writeable + '_> {
         self.to_ixdtf_writeable_with_provider(timezone, options, &*TZ_PROVIDER)

src/builtins/compiled/plain_month_day.rs

@@ -3,7 +3,7 @@ use crate::{
 };
 
 impl PlainMonthDay {
-    pub fn epoch_ns_for(&self, time_zone: &TimeZone) -> TemporalResult<EpochNanoseconds> {
+    pub fn epoch_ns_for(&self, time_zone: TimeZone) -> TemporalResult<EpochNanoseconds> {
         self.epoch_ns_for_with_provider(time_zone, &*TZ_PROVIDER)
     }
 }

src/builtins/compiled/plain_year_month.rs

@@ -3,7 +3,7 @@ use crate::{
 };
 
 impl PlainYearMonth {
-    pub fn epoch_ns_for(&self, time_zone: &TimeZone) -> TemporalResult<EpochNanoseconds> {
+    pub fn epoch_ns_for(&self, time_zone: TimeZone) -> TemporalResult<EpochNanoseconds> {
         self.epoch_ns_for_with_provider(time_zone, &*TZ_PROVIDER)
     }
 }

src/builtins/core/instant.rs

@@ -402,7 +402,7 @@ impl Instant {
 impl Instant {
     pub fn to_ixdtf_string_with_provider(
         &self,
-        timezone: Option<&TimeZone>,
+        timezone: Option<TimeZone>,
         options: ToStringRoundingOptions,
         provider: &impl TimeZoneProvider,
     ) -> TemporalResult<String> {
@@ -412,7 +412,7 @@ impl Instant {
 
     pub fn to_ixdtf_writeable_with_provider(
         &self,
-        timezone: Option<&TimeZone>,
+        timezone: Option<TimeZone>,
         options: ToStringRoundingOptions,
         provider: &impl TimeZoneProvider,
     ) -> TemporalResult<impl Writeable + '_> {

src/builtins/core/plain_month_day.rs

@@ -352,7 +352,7 @@ impl PlainMonthDay {
     // Useful for implementing HandleDateTimeTemporalYearMonth
     pub fn epoch_ns_for_with_provider(
         &self,
-        time_zone: &TimeZone,
+        time_zone: TimeZone,
         provider: &impl TimeZoneProvider,
     ) -> TemporalResult<EpochNanoseconds> {
         // 2. Let isoDateTime be CombineISODateAndTimeRecord(temporalYearMonth.[[ISODate]], NoonTimeRecord()).

src/builtins/core/plain_year_month.rs

@@ -614,7 +614,7 @@ impl PlainYearMonth {
     // Useful for implementing HandleDateTimeTemporalYearMonth
     pub fn epoch_ns_for_with_provider(
         &self,
-        time_zone: &TimeZone,
+        time_zone: TimeZone,
         provider: &impl TimeZoneProvider,
     ) -> TemporalResult<EpochNanoseconds> {
         // 2. Let isoDateTime be CombineISODateAndTimeRecord(temporalYearMonth.[[ISODate]], NoonTimeRecord()).