Refactor PtcInfo (#2625)

* Refactor `PtcInfo`

This change reduces the coupling of `PtcInfo` by moving relocation
tracking to the backend. `RelocEntry`s remains as `RelocEntry`s through
out the pipeline until it actually needs to be written to the PTC
streams. Keeping this representation makes inspecting and manipulating
relocations after compilations less painful. This is something I needed
to do to patch relocations to 0 to diff dumps.

Contributes to #1125.

* Turn `Symbol` & `RelocInfo` into readonly structs

* Add documentation to `CompiledFunction`

* Remove `Compiler.Compile<T>`

Remove `Compiler.Compile<T>` and replace it by `Map<T>` of the
`CompiledFunction` returned.

ARMeilleure/CodeGen/Linking/RelocEntry.cs

@@ -0,0 +1,38 @@
+namespace ARMeilleure.CodeGen.Linking
+{
+    /// <summary>
+    /// Represents a relocation.
+    /// </summary>
+    readonly struct RelocEntry
+    {
+        public const int Stride = 13; // Bytes.
+
+        /// <summary>
+        /// Gets the position of the relocation.
+        /// </summary>
+        public int Position { get; }
+
+        /// <summary>
+        /// Gets the <see cref="Symbol"/> of the relocation.
+        /// </summary>
+        public Symbol Symbol { get; }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RelocEntry"/> struct with the specified position and
+        /// <see cref="Symbol"/>.
+        /// </summary>
+        /// <param name="position">Position of relocation</param>
+        /// <param name="symbol">Symbol of relocation</param>
+        public RelocEntry(int position, Symbol symbol)
+        {
+            Position = position;
+            Symbol = symbol;
+        }
+
+        /// <inheritdoc/>
+        public override string ToString()
+        {
+            return $"({nameof(Position)} = {Position}, {nameof(Symbol)} = {Symbol})";
+        }
+    }
+}