Review feedback from @gregtatcam

- Rename "accountCanSpend" to "accountSpendabled".
- Change some getIssuer() local vars to use references.

include/xrpl/ledger/View.h

@@ -352,7 +352,7 @@ accountHolds(
 //
 // <-- saAmount: amount of currency held by account. May be negative.
 [[nodiscard]] STAmount
-accountCanSend(
+accountSpendable(
     ReadView const& view,
     AccountID const& account,
     Currency const& currency,
@@ -361,7 +361,7 @@ accountCanSend(
     beast::Journal j);
 
 [[nodiscard]] STAmount
-accountCanSend(
+accountSpendable(
     ReadView const& view,
     AccountID const& account,
     Issue const& issue,
@@ -369,7 +369,7 @@ accountCanSend(
     beast::Journal j);
 
 [[nodiscard]] STAmount
-accountCanSend(
+accountSpendable(
     ReadView const& view,
     AccountID const& account,
     MPTIssue const& mptIssue,
@@ -378,7 +378,7 @@ accountCanSend(
     beast::Journal j);
 
 [[nodiscard]] STAmount
-accountCanSend(
+accountSpendable(
     ReadView const& view,
     AccountID const& account,
     Asset const& asset,