[chore][pkg/ottl] Add OTTL context utilities for handling slices accessors

[edmocosta]

Description

Currently, OTTL contexts setters can received different data type when using slices, which might lead to unexpected outcomes, for example, slice setters functions can receive the following value types:

• []any when set from literals: set(string_table, ["foo", "bar"])
  • integer values within the []any are parsed as int64
• []T when copied from another path: set(slice_path, slice_path)
• pcommon.Slice when set from an map's key value: set(slice_path, resource.attributes["slice"])

Those different possibilities must be properly handled on the setter assessors, and are not obvious since the value is any-wrapped. Failing to handle all those possible types results in the path not being set or errors.

This PR adds a set of functions that helps setting and getting slices values, making it easier handling them until OTTL slice parsing is not standardized. Those functions will be especially useful for the new profile context (#37574), which needs to provide access to different pdata typed slices.

We've recently done something similar to maps (#38434).

Usage examples:

// tCtx.GetProfile().StringTable() -> pcommon.StringSlice
func accessStringTableKey[K ProfileContext](ctx context.Context, keys []ottl.Key[K]) ottl.StandardGetSetter[K] {
	return ottl.StandardGetSetter[K]{
		Getter: func(_ context.Context, tCtx K) (any, error) {
			return ctxutil.GetCommonTypedSliceValue[K, string](ctx, tCtx, tCtx.GetProfile().StringTable(), keys)
		},
		Setter: func(_ context.Context, tCtx K, val any) error {
			return ctxutil.SetCommonTypedSliceValue[K, string](ctx, tCtx, tCtx.GetProfile().StringTable(), keys, val)
		},
	}
}

func accessStringTable[K ProfileContext]() ottl.StandardGetSetter[K] {
	return ottl.StandardGetSetter[K]{
		Getter: func(_ context.Context, tCtx K) (any, error) {
			return tCtx.GetProfile().StringTable().AsRaw(), nil
		},
		Setter: func(_ context.Context, tCtx K, val any) error {
			return ctxutil.SetCommonTypedSliceValues[string](tCtx.GetProfile().StringTable(), val)
		},
	}
}

// *Int* function versions also handle type conversions and ensure returned values are compatible with OTTL defaults (int64).
// tCtx.GetProfile().LocationIndices() -> pcommon.Int32Slice
func accessLocationIndicesKey[K ProfileContext](ctx context.Context, keys []ottl.Key[K]) ottl.StandardGetSetter[K] {
	return ottl.StandardGetSetter[K]{
		Getter: func(_ context.Context, tCtx K) (any, error) {
			return ctxutil.GetCommonIntSliceValue[K, int32](ctx, tCtx, tCtx.GetProfile().LocationIndices(), keys)
		},
		Setter: func(_ context.Context, tCtx K, val any) error {
			return ctxutil.SetCommonIntSliceValue[K, int32](ctx, tCtx, tCtx.GetProfile().LocationIndices(), keys, val)
		},
	}
}

func accessLocationIndices[K ProfileContext]() ottl.StandardGetSetter[K] {
	return ottl.StandardGetSetter[K]{
		Getter: func(_ context.Context, tCtx K) (any, error) {
			return ctxutil.GetCommonIntSliceValues[int32](tCtx.GetProfile().LocationIndices()), nil
		},
		Setter: func(_ context.Context, tCtx K, val any) error {
			return ctxutil.SetCommonIntSliceValues[int32](tCtx.GetProfile().LocationIndices(), val)
		},
	}
}

Testing

• Unit tests

[edmocosta]

@TylerHelmuth @evan-bradley @djaglowski could you please review? Those functions would be especially useful for the profile context #37574. Thanks.