Port System.Collections docs for .NET 9 APIs

[carlossanlop]

Below is the list of APIs that still show up as undocumented in dotnet-api-docs and were introduced in .NET 9.

Full porting instructions can be found in the main issue.

This task needs to be finished the day before the RC2 snap (September 15th).

RC1 APIs as of 2024/10/01: #105976 (comment)

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-collections
See info in area-owners.md if you want to be subscribed.

[carlossanlop]

Here's a PR that ports some that we missed in the first pass: dotnet/dotnet-api-docs#10209

[carlossanlop]

P7 Undoc APIs as of 08/20:

Summary	Parameters	TypeParameters	ReturnValue	API
Missing	Missing	Missing	Missing	M:System.Collections.Concurrent.ConcurrentDictionary2.TryGetAlternateLookup1(System.Collections.Concurrent.ConcurrentDictionary2.AlternateLookup{0,1,0}@)
Present	NA	Missing	NA	T:System.Collections.Concurrent.ConcurrentDictionary2.AlternateLookup1
Present	Present	NA	Missing	M:System.Collections.Concurrent.ConcurrentDictionary2.AlternateLookup1.TryGetValue(2,0@,1@)
Present	Present	NA	Missing	M:System.Collections.Concurrent.ConcurrentDictionary2.AlternateLookup1.TryGetValue(2,1@)
Missing	Missing	Missing	Missing	M:System.Collections.Frozen.FrozenDictionary2.TryGetAlternateLookup1(System.Collections.Frozen.FrozenDictionary2.AlternateLookup{0,1,0}@)
Present	NA	Missing	NA	T:System.Collections.Frozen.FrozenDictionary2.AlternateLookup1
Present	Present	NA	Missing	M:System.Collections.Frozen.FrozenDictionary2.AlternateLookup1.TryGetValue(2,1@)
Missing	Missing	Missing	Missing	M:System.Collections.Frozen.FrozenSet1.TryGetAlternateLookup1(System.Collections.Frozen.FrozenSet1.AlternateLookup{0,0}@)
Present	NA	Missing	NA	T:System.Collections.Frozen.FrozenSet1.AlternateLookup1
Present	NA	Missing	NA	T:System.Collections.Generic.Dictionary2.AlternateLookup1
Present	Present	NA	Missing	M:System.Collections.Generic.Dictionary2.AlternateLookup1.TryGetValue(2,1@)
Present	Present	NA	Missing	M:System.Collections.Generic.Dictionary2.AlternateLookup1.TryGetValue(2,0@,1@)
Present	NA	Missing	NA	T:System.Collections.Generic.HashSet1.AlternateLookup1
Present	Missing	NA	Present	M:System.Collections.Generic.OrderedDictionary2.KeyCollection.Contains(0)

[eiriktsarpalis]

With the exception of all the TryGetValue methods, everything else in this table appears to be documented in source, for example the entry in the first row:

runtime/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs

Lines 247 to 258 in d756692

	/// <summary>
	/// Gets an instance of a type that may be used to perform operations on a <see cref="ConcurrentDictionary{TKey, TValue}"/>
	/// using a <typeparamref name="TAlternateKey"/> as a key instead of a <typeparamref name="TKey"/>.
	/// </summary>
	/// <typeparam name="TAlternateKey">The alternate type of a key for performing lookups.</typeparam>
	/// <param name="lookup">The created lookup instance when the method returns true, or a default instance that should not be used if the method returns false.</param>
	/// <returns>true if a lookup could be created; otherwise, false.</returns>
	/// <remarks>
	/// This instance must be using a comparer that implements <see cref="IAlternateEqualityComparer{TAlternateKey, TKey}"/> with
	/// <typeparamref name="TAlternateKey"/> and <typeparamref name="TKey"/>. If it doesn't, the method will return false.
	/// </remarks>
	public bool TryGetAlternateLookup<TAlternateKey>(out AlternateLookup<TAlternateKey> lookup) where TAlternateKey : notnull, allows ref struct

Running the tool again locally seems to be skipping over these missing docs as well. @carlossanlop any suggestions or should I just port the missing docs manually?