ssa: removes map use for Value aliasing

[mathetake]

This improves the compilation perf by up to ~30% without
runtime perf impacts.

goos: darwin
goarch: arm64
pkg: github.com/tetratelabs/wazero/internal/integration_test/stdlibs
                                            │   old.txt    │              new.txt               │
                                            │    sec/op    │   sec/op     vs base               │
Zig/Compile/test-opt.wasm-10                    2.683 ± 1%    2.591 ± 1%   -3.44% (p=0.002 n=6)
Zig/Run/test-opt.wasm-10                        18.75 ± 0%    19.03 ± 1%   +1.48% (p=0.004 n=6)
Zig/Compile/test.wasm-10                        3.529 ± 0%    3.516 ± 1%        ~ (p=0.180 n=6)
Zig/Run/test.wasm-10                            19.55 ± 2%    19.48 ± 1%        ~ (p=0.310 n=6)
TinyGo/Compile/container_heap.test-10          298.1m ± 1%   210.1m ± 0%  -29.51% (p=0.002 n=6)
TinyGo/Run/container_heap.test-10              14.59m ± 2%   14.55m ± 1%        ~ (p=0.310 n=6)
TinyGo/Compile/container_list.test-10          290.6m ± 0%   208.6m ± 0%  -28.20% (p=0.002 n=6)
TinyGo/Run/container_list.test-10              14.47m ± 1%   14.40m ± 0%        ~ (p=0.132 n=6)
TinyGo/Compile/container_ring.test-10          286.4m ± 0%   205.1m ± 0%  -28.42% (p=0.002 n=6)
TinyGo/Run/container_ring.test-10              14.36m ± 1%   14.42m ± 1%        ~ (p=0.180 n=6)
TinyGo/Compile/crypto_des.test-10              296.6m ± 0%   214.2m ± 2%  -27.77% (p=0.002 n=6)
TinyGo/Run/crypto_des.test-10                  18.70m ± 4%   18.64m ± 0%        ~ (p=0.132 n=6)
TinyGo/Compile/crypto_md5.test-10              295.8m ± 5%   211.4m ± 0%  -28.53% (p=0.002 n=6)
TinyGo/Run/crypto_md5.test-10                  21.72m ± 1%   20.67m ± 1%   -4.85% (p=0.002 n=6)
TinyGo/Compile/crypto_rc4.test-10              291.4m ± 2%   203.4m ± 0%  -30.20% (p=0.002 n=6)
TinyGo/Run/crypto_rc4.test-10                  161.0m ± 1%   160.7m ± 1%        ~ (p=0.818 n=6)
TinyGo/Compile/crypto_sha1.test-10             296.0m ± 0%   211.9m ± 1%  -28.43% (p=0.002 n=6)
TinyGo/Run/crypto_sha1.test-10                 16.14m ± 1%   16.17m ± 1%        ~ (p=0.485 n=6)
TinyGo/Compile/crypto_sha256.test-10           301.0m ± 1%   216.1m ± 1%  -28.21% (p=0.002 n=6)
TinyGo/Run/crypto_sha256.test-10               16.21m ± 1%   16.27m ± 1%        ~ (p=0.310 n=6)
Wasip1/Compile/src_archive_tar.test-10          1.596 ± 0%    1.490 ± 0%   -6.63% (p=0.002 n=6)
Wasip1/Run/src_archive_tar.test-10             396.5m ± 0%   396.5m ± 1%        ~ (p=0.818 n=6)
Wasip1/Compile/src_bufio.test-10                1.089 ± 0%    1.008 ± 0%   -7.44% (p=0.002 n=6)
Wasip1/Run/src_bufio.test-10                   121.4m ± 0%   121.5m ± 0%        ~ (p=0.240 n=6)
Wasip1/Compile/src_bytes.test-10                1.127 ± 0%    1.038 ± 0%   -7.91% (p=0.002 n=6)
Wasip1/Run/src_bytes.test-10                   468.1m ± 1%   466.8m ± 1%        ~ (p=0.132 n=6)
Wasip1/Compile/src_context.test-10              1.213 ± 1%    1.119 ± 0%   -7.76% (p=0.002 n=6)
Wasip1/Run/src_context.test-10                 33.69m ± 1%   33.57m ± 0%   -0.33% (p=0.026 n=6)
Wasip1/Compile/src_encoding_ascii85.test-10    979.9m ± 0%   905.5m ± 0%   -7.59% (p=0.002 n=6)
Wasip1/Run/src_encoding_ascii85.test-10        7.320m ± 1%   7.324m ± 3%        ~ (p=0.589 n=6)
Wasip1/Compile/src_encoding_asn1.test-10        1.128 ± 1%    1.043 ± 0%   -7.48% (p=0.002 n=6)
Wasip1/Run/src_encoding_asn1.test-10           8.221m ± 2%   8.239m ± 1%        ~ (p=0.394 n=6)
Wasip1/Compile/src_encoding_base32.test-10    1019.3m ± 1%   940.4m ± 0%   -7.74% (p=0.002 n=6)
Wasip1/Run/src_encoding_base32.test-10         28.57m ± 1%   28.78m ± 0%   +0.74% (p=0.041 n=6)
Wasip1/Compile/src_encoding_base64.test-10    1024.8m ± 1%   945.4m ± 0%   -7.75% (p=0.002 n=6)
Wasip1/Run/src_encoding_base64.test-10         11.78m ± 1%   11.80m ± 4%        ~ (p=0.589 n=6)

#2182