script: Properly implement supportedAlgorithms of WebCrypto (#41563)

WebCrypto API has an internal object `supportedAlgorithms`
<https://w3c.github.io/webcrypto/#dfn-supportedAlgorithms> that maps the
all supported algorithms and operations to their desired IDL dictionary
types. It is mainly used by the "normalize an algorithm" algorithm
<https://w3c.github.io/webcrypto/#algorithm-normalization-normalize-an-algorithm>.
We currently implement it as a large `match` block in the
`normalize_algorithm` function.

This patch properly implements the internal object `supportedAlgorithms`
as a new enum type `SupportedAlgorithm`.

By doing so, we can reduce a lot of string comparison to enum matching,
which can be done faster. This patch also separates the dictionary
conversion away from the `match` block to make our code cleaner.
Furthermore, the `exportKey()` method can now utilize the new
`SupportedAlgorithm` to properly check against the algorithm
registration, instead of hard-coding an list of unsupported algorithms
by itself.

Testing: Refactoring. Existing tests suffice.

---------

Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>

components/script/dom/subtlecrypto/rsa_oaep_operation.rs

@@ -405,7 +405,7 @@ pub(crate) fn import_key(
                 // set to hash and op set to digest.
                 let normalized_hash = normalize_algorithm(
                     cx,
-                    &Operation::Digest,
+                    Operation::Digest,
                     &AlgorithmIdentifier::String(DOMString::from(hash)),
                     can_gc,
                 )?;

components/script/dom/subtlecrypto/rsa_pss_operation.rs

@@ -421,7 +421,7 @@ pub(crate) fn import_key(
                 // set to hash and op set to digest.
                 let normalized_hash = normalize_algorithm(
                     cx,
-                    &Operation::Digest,
+                    Operation::Digest,
                     &AlgorithmIdentifier::String(DOMString::from(hash)),
                     can_gc,
                 )?;

components/script/dom/subtlecrypto/rsassa_pkcs1_v1_5_operation.rs

@@ -385,7 +385,7 @@ pub(crate) fn import_key(
                 // set to hash and op set to digest.
                 let normalized_hash = normalize_algorithm(
                     cx,
-                    &Operation::Digest,
+                    Operation::Digest,
                     &AlgorithmIdentifier::String(DOMString::from(hash)),
                     can_gc,
                 )?;